Apparatus and method for treating an interval of a wellbore

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

0001This application is a continuation application of Ser. No. 10/160,216 filed May 31, 2002 and a continuation-in-part application of Ser. No. 10/796,467 filed Mar. 9, 2004 which is a continuation application of Ser. No. 09/927,217 filed Aug. 10, 2001, now U.S. Pat. No. 6,702,018, which is a continuation-in-part application of Ser. No. 09/800,199 filed Mar. 6, 2001, now U.S. Pat. No. 6,557,634, each of which is incorporated by reference for all purposes.

TECHNICAL FIELD OF THE INVENTION

0002This invention relates in general to preventing the production of particulate materials through a wellbore traversing an unconsolidated or loosely consolidated subterranean formation and, in particular to, an apparatus and method for obtaining a substantially complete gravel pack within an interval of the wellbore.

BACKGROUND OF THE INVENTION

0003Without limiting the scope of the present invention, its background is described with reference to the production of hydrocarbons through a wellbore traversing an unconsolidated or loosely consolidated formation, as an example.

0004It is well known in the subterranean well drilling and completion art that particulate materials such as sand may be produced during the production of hydrocarbons from a well traversing an unconsolidated or loosely consolidated subterranean formation. Numerous problems may occur as a result of the production of such particulate. For example, the particulate causes abrasive wear to components within the well, such as tubing, pumps and valves. In addition, the particulate may partially or fully clog the well creating the need for an expensive workover. Also, if the particulate matter is produced to the surface, it must be removed from the hydrocarbon fluids by processing equipment at the surface.

0005One method for preventing the production of such particulate material to the surface is gravel packing the well adjacent the unconsolidated or loosely consolidated production interval. In a typical gravel pack completion, a sand control screen is lowered into the wellbore on a work string to a position proximate the desired production interval. A fluid slurry including a liquid carrier and a particulate material known as gravel is then pumped down the work string and into the well annulus formed between the sand control screen and the perforated well casing or open hole production zone.

0006The liquid carrier either flows into the formation or returns to the surface by flowing through the sand control screen or both. In either case, the gravel is deposited around the sand control screen to form a gravel pack, which is highly permeable to the flow of hydrocarbon fluids but blocks the flow of the particulate carried in the hydrocarbon fluids. As such, gravel packs can successfully prevent the problems associated with the production of particulate materials from the formation.

0007It has been found, however, that a complete gravel pack of the desired production interval is difficult to achieve particularly in long or inclined/horizontal production intervals. These incomplete packs are commonly a result of the liquid carrier entering a permeable portion of the production interval causing the gravel to form a sand bridge in the annulus. Thereafter, the sand bridge prevents the slurry from flowing to the remainder of the annulus which, in turn, prevents the placement of sufficient gravel in the remainder of the annulus.

0008Prior art devices and methods have been developed which attempt to overcome this sand bridge problem. For example, attempts have been made to use devices having perforated shunt tubes or bypass conduits that extend along the length of the sand control screen to provide an alternate path for the fluid slurry around the sand bridge. It has been found, however, that shunt tubes installed on the exterior of sand control screens are susceptible to damage during installation and may fail during a gravel pack operation. In addition, it has been found that it is difficult and time consuming to make all of the necessary fluid connections between the numerous joints of shunt tubes required for typical production intervals.

0009Therefore a need has arisen for an apparatus and method for gravel packing a production interval traversed by a wellbore that overcomes the problems created by sand bridges. A need has also arisen for such an apparatus that is not susceptible to damage during installation or failure during use. Further, a need has arisen for such an apparatus that is not difficult or time consuming to assemble.

SUMMARY OF THE INVENTION

0010The present invention disclosed herein comprises an apparatus and method for gravel packing a production interval of a wellbore that traverses an unconsolidated or loosely consolidated formation that overcomes the problems created by the development of a sand bridge between a sand control screen and the wellbore. Importantly, the apparatus of the present invention is not susceptible to damage during installation or failure during use and is not difficult or time consuming to assemble.

0011The apparatus for gravel packing an interval of a wellbore of the present invention comprises an outer tubular forming a first annulus with the wellbore and a sand control screen disposed within the outer tubular forming a second annulus therebetween. Together, the sand control screen and the outer tubular of the present invention are assembled at the surface and run downhole to a location proximate the production interval. The outer tubular includes a plurality of openings that allow for the production of fluids therethrough and plurality of outlets that allow the distribution of a fluid slurry containing gravel therethrough.

0012In the volume within the second annulus between the sand control screen and the outer tubular there are one or more channels that define axially extending slurry passageways with sheet members positioned between the channels and the sand control screen. The sheet members create a barrier to the flow of fluids between the channels and the sand control screen. The volume within the second annulus between adjacent channels forms axially extending production pathways. The channels prevent fluid communication between the production pathways and the slurry passageways. In addition, isolation members at either end of a section of the apparatus of the present invention define the axial boundaries of the production pathways.

0013As such, when a fluid slurry containing gravel is injected through the slurry passageways, the fluid slurry exits the slurry passageways through outlets in the channels and the outer tubular leaving a first portion of the gravel in the first annulus. Thereafter, the fluid slurry enters the openings in the outer tubular leaving a second portion of the gravel in the production pathways. Thus, when formation fluids are produced, the formation fluids travel radially through the production pathways by entering the openings in the outer tubular and exiting the production pathways through the sand control screen. The formation fluids pass through the first portion of the gravel in the first annulus prior to entry into the production pathways, which contains the second portion of the gravel, both of which filter out the particulate materials in the formation fluids. Formation fluids are prevented, however, from traveling radially through the slurry passageways as the sheet members prevent such flow.

0014In a typical gravel packing operation using the apparatus for gravel packing an interval of a wellbore of the present invention, the first annulus between the outer tubular and the wellbore may serve as a primary path for delivery of a fluid slurry. This region serves as the primary path as it provides the path of least resistance to the flow of the fluid slurry. When the primary path becomes blocked by sand bridge formation, the production pathways of the present invention serves as independent secondary paths for delivery of the fluid slurry. The production pathways serve as the secondary paths as they provide the paths of second least resistance to the flow of the fluid slurry. When the primary path and secondary paths become blocked by sand bridge formation, the slurry passageways serve as independent tertiary paths for delivery of the fluid slurry. The slurry passageways serve as the tertiary paths as they provide the paths of greatest resistance to the flow of the fluid slurry but are least likely to have sand bridge formation therein due to the high velocity of the fluid slurry flowing therethrough and their substantial isolation from the formation.

0015Commonly, more than one section of the apparatus for gravel packing an interval of a wellbore must be coupled together to achieve a length sufficient to gravel pack an entire production interval. In such cases, multiple sections of the apparatus of the present invention are coupled together, for example, via a threaded connection. Also, in such cases, the slurry passageways of the various sections are in fluid communication with one another allowing an injected fluid slurry to flow from one such apparatus to the next, while the production pathways of the various sections are in fluid isolation from one another.

0016In a method for gravel packing an interval of a wellbore of the present invention, the method comprises providing a wellbore that traverses a formation, either open hole or cased, perforating the casing, in the cased hole embodiment, proximate the formation to form a plurality of perforations, locating a gravel packing apparatus including a sand control screen within the wellbore proximate the formation to form a first annulus between the gravel packing apparatus and the wellbore and a second annulus between the sand control screen and the outer tubular, injecting a fluid slurry containing gravel through slurry passageways formed between sheet members and channels with the second annulus such that the fluid slurry exits through the outlets of the channels and the outer tubular into the first annulus, depositing a first portion of the gravel in the first annulus, depositing a second portion of the gravel in the production pathways by returning a portion of the fluid slurry through openings in the outer tubular and terminating the injection when the first annulus and the production pathways are substantially completely packed with gravel.

0017In addition to injecting the fluid slurry containing gravel through the slurry passageways, in some embodiments, the fluid slurry may also be injected down the first annulus. In this case, the method also involves injecting a fluid slurry containing gravel into a primary path defined by the first annulus, diverting the fluid slurry containing gravel into a secondary path defined by the production pathways if the primary path becomes blocked, diverting the fluid slurry containing gravel into a tertiary path defined by the slurry passageways if the primary and secondary paths become blocked and terminating the injecting when the interval is substantially completely packed with the gravel.

BRIEF DESCRIPTION OF THE DRAWINGS

0018For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which:

0019<figref idref="DRAWINGS">FIG. 1</figref> is a schematic illustration of an offshore oil and gas platform operating an apparatus for gravel packing an interval of a wellbore of the present invention;

0020<figref idref="DRAWINGS">FIG. 2</figref> is partial cut away view of an apparatus for gravel packing an interval of a wellbore of the present invention in position around a sand control screen;

0021<figref idref="DRAWINGS">FIG. 3</figref> is partial cut away view of an apparatus for gravel packing an interval of a wellbore of the present invention in position around a sand control screen;

0022<figref idref="DRAWINGS">FIG. 4</figref> is a side view of portions of two sections of an apparatus for gravel packing an interval of a wellbore of the present invention that are coupled together;

0023<figref idref="DRAWINGS">FIG. 5</figref> is a side view of portions of two sections of a sand control screen for an apparatus for gravel packing an interval of a wellbore of the present invention that are coupled together;

0024<figref idref="DRAWINGS">FIG. 6</figref> is a cross sectional view of an apparatus for gravel packing an interval of a wellbore of the present invention taken along line <b>6</b>-<b>6</b> of <figref idref="DRAWINGS">FIGS. 4 and 5</figref>;

0025<figref idref="DRAWINGS">FIG. 7</figref> is a cross sectional view of an apparatus for gravel packing an interval of a wellbore of the present invention taken along line <b>7</b>-<b>7</b> of <figref idref="DRAWINGS">FIGS. 4 and 5</figref>;

0026<figref idref="DRAWINGS">FIG. 8</figref> is a cross sectional view of an apparatus for gravel packing an interval of a wellbore of the present invention taken along line <b>8</b>-<b>8</b> of <figref idref="DRAWINGS">FIGS. 4 and 5</figref>;

0027<figref idref="DRAWINGS">FIG. 9</figref> is a cross sectional view of an apparatus for gravel packing an interval of a wellbore of the present invention taken along line <b>9</b>-<b>9</b> of <figref idref="DRAWINGS">FIGS. 4 and 5</figref>;

0028<figref idref="DRAWINGS">FIG. 10</figref> is a side view of two channels connected together in an area between adjacent screen sections of an apparatus for gravel packing an interval of a wellbore of the present invention;

0029<figref idref="DRAWINGS">FIG. 11</figref> is a cross sectional view of a spacer member for positioning between adjacent screen sections of an apparatus for gravel packing an interval of a wellbore of the present invention;

0030<figref idref="DRAWINGS">FIG. 12</figref> is a cross sectional view of a spacer member for positioning between adjacent screen sections of an apparatus for gravel packing an interval of a wellbore of the present invention;

0031<figref idref="DRAWINGS">FIG. 13</figref> is a cross sectional view of a spacer member for positioning between adjacent screen sections of an apparatus for gravel packing an interval of a wellbore of the present invention;

0032<figref idref="DRAWINGS">FIG. 14</figref> is a half sectional view depicting the operation of an apparatus for gravel packing an interval of a wellbore of the present invention; and

0033<figref idref="DRAWINGS">FIG. 15</figref> is a half sectional view depicting the operation of another embodiment of an apparatus for gravel packing an interval of a wellbore of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

0034While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the present invention.

0035Referring initially to <figref idref="DRAWINGS">FIG. 1</figref>, several apparatuses for gravel packing an interval of a wellbore operating from an offshore oil and gas platform are schematically illustrated and generally designated <b>10</b>. A semi-submersible platform <b>12</b> is centered over a submerged oil and gas formation <b>14</b> located below sea floor <b>16</b>. A subsea conduit <b>18</b> extends from deck <b>20</b> of platform <b>12</b> to wellhead installation <b>22</b> including blowout preventers <b>24</b>. Platform <b>12</b> has a hoisting apparatus <b>26</b> and a derrick <b>28</b> for raising and lowering pipe strings such as work string <b>30</b>.

0036A wellbore <b>32</b> extends through the various earth strata including formation <b>14</b>. A casing <b>34</b> is cemented within wellbore <b>32</b> by cement <b>36</b>. Work string <b>30</b> includes various tools including apparatuses <b>38</b>, <b>40</b>, <b>42</b> for gravel packing an interval of wellbore <b>32</b> adjacent to formation <b>14</b> between packers <b>44</b>, <b>46</b> and into annular region <b>48</b>. When it is desired to gravel pack annular region <b>48</b>, work string <b>30</b> is lowered through casing <b>34</b> until apparatuses <b>38</b>, <b>40</b>, <b>42</b> are positioned adjacent to formation <b>14</b> including perforations <b>50</b>. Thereafter, a fluid slurry including a liquid carrier and a particulate material such as sand, gravel or proppants is pumped down work string <b>30</b>.

0037As explained in more detail below, the fluid slurry may be injected entirely into apparatus <b>38</b> and sequentially flow through apparatuses <b>40</b>, <b>42</b>. During this process, portions of the fluid slurry exit each apparatus <b>38</b>, <b>40</b>, <b>42</b> such that the fluid slurry enters annular region <b>48</b>. Once in annular region <b>48</b>, a portion of the gravel in the fluid slurry is deposited therein. Some of the liquid carrier may enter formation <b>14</b> through perforation <b>50</b> while the remainder of the fluid carrier, along with some of the gravel, reenters certain sections of apparatuses <b>38</b>, <b>40</b>, <b>42</b> depositing gravel in those sections. As a sand control screen (not pictured) is positioned within apparatuses <b>38</b>, <b>40</b>, <b>42</b>, the gravel remaining in the fluid slurry is disallowed from further migration. The liquid carrier, however, can travel through the sand control screen, into work string <b>30</b> and up to the surface in a known manner, such as through a wash pipe and into the annulus <b>52</b> above packer <b>44</b>. The fluid slurry is pumped down work string <b>30</b> through apparatuses <b>38</b>, <b>40</b>, <b>42</b> until annular section <b>48</b> surrounding apparatuses <b>38</b>, <b>40</b>, <b>42</b> and portions of apparatuses <b>38</b>, <b>40</b>, <b>42</b> are filled with gravel.

0038Alternatively, instead of injecting the entire stream of fluid slurry into apparatuses <b>38</b>, <b>40</b>, <b>42</b>, all or a portion of the fluid slurry could be injected directly into annular region <b>48</b> in a known manner such as through a crossover tool (not pictured) which allows the slurry to travel from the interior of work string <b>30</b> to the exterior of work string <b>30</b>. Again, once this portion of the fluid slurry is in annular region <b>48</b>, a portion of the gravel in the fluid slurry is deposited in annular region <b>48</b>. Some of the liquid carrier may enter formation <b>14</b> through perforation <b>50</b> while the remainder of the fluid carrier along with some of the gravel enters certain sections of apparatuses <b>38</b>, <b>40</b>, <b>42</b> filling those sections with gravel. The sand control screen (not pictured) within apparatuses <b>38</b>, <b>40</b>, <b>42</b> disallows further migration of the gravel but allows the liquid carrier to travel therethrough into work string <b>30</b> and up to the surface. If the fluid slurry is injected directly into annular region <b>48</b> and a sand bridge forms, the fluid slurry is diverted into apparatuses <b>38</b>, <b>40</b>, <b>42</b> to bypass this sand bridge such that a complete pack can nonetheless be achieved. The fluid slurry entering apparatuses <b>38</b>, <b>40</b>, <b>42</b> may enter apparatuses <b>38</b>, <b>40</b>, <b>42</b> proximate work string <b>30</b> or may enter apparatuses <b>38</b>, <b>40</b>, <b>42</b> from annular region <b>48</b> via one or more inlets on the exterior of one or more of the apparatuses <b>38</b>, <b>40</b>, <b>42</b>. These inlets may include pressure actuated devices, such as valves, rupture disks and the like disposed therein to regulate the flow of the fluid slurry therethrough.

0039Even though <figref idref="DRAWINGS">FIG. 1</figref> depicts a vertical well, it should be noted by one skilled in the art that the apparatus for gravel packing an interval of a wellbore of the present invention is equally well-suited for use in deviated wells, inclined wells or horizontal wells. Also, even though <figref idref="DRAWINGS">FIG. 1</figref> depicts an offshore operation, it should be noted by one skilled in the art that the apparatus for gravel packing an interval of a wellbore of the present invention is equally well-suited for use in onshore operations.

0040Referring now to <figref idref="DRAWINGS">FIG. 2</figref>, therein is depicted a partial cut away view of an apparatus for gravel packing an interval of a wellbore of the present invention that is generally designated <b>60</b>. Apparatus <b>60</b> has an outer tubular <b>62</b> that includes a plurality of openings <b>64</b> that are substantially evenly distributed around and along the length of outer tubular <b>62</b>. In addition, outer tubular <b>62</b> includes a plurality outlets <b>66</b>. For reasons that will become apparent to those skilled in the art, the density of opening <b>64</b> of outer tubular <b>62</b> is much greater than the density of outlets <b>66</b> of outer tubular <b>62</b>. Also, it should be noted by those skilled in the art that even though <figref idref="DRAWINGS">FIG. 2</figref> has depicted openings <b>64</b> and outlets <b>66</b> as being circular, other shaped openings may alternatively be used without departing from the principles of the present invention. Likewise, even though <figref idref="DRAWINGS">FIG. 2</figref> has depicted openings <b>64</b> as being smaller than outlets <b>66</b>, openings <b>64</b> could alternatively be larger than or the same size as outlets <b>66</b> without departing from the principles of the present invention. In addition, the exact number, size and shape of openings <b>64</b> are not critical to the present invention, so long as sufficient area is provided for fluid production therethrough and the integrity of outer tubular <b>62</b> is maintained.

0041Disposed within outer tubular <b>62</b> is a sand control screen <b>70</b>. Sand control screen <b>70</b> includes a base pipe <b>72</b> that has a plurality of openings <b>74</b> which allow the flow of production fluids into the production tubing. The exact number, size and shape of openings <b>74</b> are not critical to the present invention, so long as sufficient area is provided for fluid production and the integrity of base pipe <b>72</b> is maintained.

0042Spaced around base pipe <b>72</b> is a plurality of ribs <b>76</b>. Ribs <b>76</b> are generally symmetrically distributed about the axis of base pipe <b>72</b>. Ribs <b>76</b> are depicted as having a cylindrical cross section, however, it should be understood by one skilled in the art that ribs <b>76</b> may alternatively have a rectangular or triangular cross section or other suitable geometry. Additionally, it should be understood by one skilled in the art that the exact number of ribs <b>76</b> will be dependent upon the diameter of base pipe <b>72</b> as well as other design characteristics that are well known in the art.

0043Wrapped around ribs <b>76</b> is a screen wire <b>78</b>. Screen wire <b>78</b> forms a plurality of turns, such as turn <b>80</b>, turn <b>82</b> and turn <b>84</b>. Between each of the turns is a gap through which formation fluids flow. The number of turns and the gap between the turns are determined based upon the characteristics of the formation from which fluid is being produced and the size of the gravel to be used during the gravel packing operation. Together, ribs <b>76</b> and screen wire <b>78</b> may form a sand control screen jacket which is attached to base pipe <b>72</b> by welding or other suitable techniques.

0044Disposed within an annulus <b>86</b> on opposite sides of one another and between outer tubular <b>62</b> and sand control screen <b>70</b> is a pair of channels <b>88</b>, only one being visible. Channels <b>88</b> include a web <b>90</b> and a pair of oppositely disposed sides <b>92</b> each having an end <b>94</b>. Ends <b>94</b> are attached to a sheet member <b>96</b> and, in turn, to sand control screen <b>70</b> by, for example, welding or other suitable techniques. Channels <b>88</b> includes a plurality of outlets <b>98</b> that are substantially aligned with outlets <b>66</b> of outer tubular <b>62</b>. Together, channels <b>88</b> and sheet members <b>96</b> define slurry passageways <b>100</b>. Between channels <b>88</b> are production pathways <b>102</b> which are defined by the radial boundaries of outer tubular <b>62</b> and sand control screen <b>70</b> and the circumferential boundaries of sides <b>92</b> of channels <b>88</b>. Slurry passageways <b>100</b> and production pathways <b>102</b> are in fluid isolation from one another.

0045It should be understood by those skilled in the art that while <figref idref="DRAWINGS">FIG. 2</figref> has depicted a wire wrapped sand control screen, other types of filter media could alternatively be used in conjunction with the apparatus of the present invention, including, but not limited to, a fluid-porous, particulate restricting, sintered metal material such as a plurality of layers of a wire mesh that are sintered together to form a porous sintered wire mesh screen designed to allow fluid flow therethrough but prevent the flow of particulate materials of a predetermined size from passing therethrough.

0046More specifically and referring now to <figref idref="DRAWINGS">FIG. 3</figref>, therein is depicted a partial cut away view of an apparatus for gravel packing an interval of a wellbore of the present invention that is generally designated <b>110</b>. Apparatus <b>110</b> has an outer tubular <b>112</b> that includes a plurality of openings <b>114</b> that are substantially evenly distributed around and along the length of outer tubular <b>112</b>, which allow the flow of production fluids therethrough. In addition, outer tubular <b>112</b> includes a plurality of outlets <b>116</b>.

0047Disposed within outer tubular <b>112</b> is a sand control screen assembly <b>118</b>. Sand control screen assembly <b>118</b> includes a base pipe <b>120</b> that has a plurality of openings <b>122</b> which allow the flow of production fluids into the production tubing. The exact number, size and shape of openings <b>122</b> are not critical to the present invention, so long as sufficient area is provided for fluid production and the integrity of base pipe <b>120</b> is maintained.

0048Positioned around base pipe <b>120</b> is a fluid-porous, particulate restricting, sintered metal material such as plurality of layers of a wire mesh that are sintered together to form a porous sintered wire mesh screen <b>124</b>. Screen <b>124</b> is designed to allow fluid flow therethrough but prevent the flow of particulate materials of a predetermined size from passing therethrough. The layers of wire mesh may include drain layers that have a mesh size that is larger than the mesh size of the filter layers. For example, a drain layer may preferably be positioned as the outermost layer and the innermost layer of wire mesh screen <b>124</b> with the filter layer or layers positioned therebetween. Positioned around screen <b>124</b> is a screen wrapper <b>126</b> that has a plurality of openings <b>128</b> which allow the flow of production fluids therethrough. The exact number, size and shape of openings <b>128</b> is not critical to the present invention, so long as sufficient area is provided for fluid production and the integrity of screen wrapper <b>126</b> is maintained. Typically, various sections of screen <b>124</b> and screen wrapper <b>126</b> are manufactured together as a unit by, for example, sintering a number layers of wire mesh that form screen <b>124</b> together with screen wrapper <b>126</b>, then rolling the unit into a tubular configuration. The two ends of the tubular unit are then seam welded together. Several tubular units of the screen and screen wrapper combination are placed over each joint of base pipe <b>120</b> and secured thereto by welding or other suitable technique, as will be explained in greater detail below.

0049Disposed in annulus <b>130</b> between outer tubular <b>112</b> and sand control screen <b>118</b> and on opposite sides of each other is a pair of channels <b>132</b>, only one channel <b>132</b> being visible. Channels <b>132</b> include a web <b>134</b> and a pair of oppositely disposed sides <b>136</b> each having an end <b>138</b>. Ends <b>138</b> are attached to a sheet member <b>140</b> and, in turn, to screen wrapper <b>126</b> by welding or other suitable technique. Channels <b>132</b> include a plurality of outlets <b>142</b> that are substantially aligned with outlets <b>116</b> of outer tubular <b>112</b> and are preferably formed at the same time by drilling or other suitable technique once gravel packing apparatus <b>110</b> is assembled. Together, channels <b>132</b> and sheet members <b>140</b> form slurry passageways <b>144</b>. Also, channels <b>132</b> define the circumferential boundary between a slurry passageway <b>144</b> and production pathways <b>146</b>.

0050Referring now to <figref idref="DRAWINGS">FIGS. 4 and 5</figref>, therein are depicted portions of two joints of outer tubulars designated <b>150</b> and <b>152</b> and corresponding portions of two joints of sand control screens designated <b>154</b> and <b>156</b>, respectively. Outer tubular <b>150</b> has a plurality of openings <b>158</b> and several outlets <b>160</b>. Likewise, outer tubular <b>152</b> has a plurality of openings <b>162</b> and several outlets <b>164</b>, which are not visible in <figref idref="DRAWINGS">FIG. 4</figref>.

0051As should become apparent to those skilled in the art, even though <figref idref="DRAWINGS">FIG. 4</figref> depicts outer tubular <b>150</b> and outer tubular <b>152</b> at a ninety-degree circumferential phase shift relative to one another, any degree of circumferential phase shift is acceptable using the present invention as the relative circumferential positions of adjoining joints of the apparatus for gravel packing an interval of a wellbore of the present invention does not affect the operation of the present invention. As such, the mating of adjoining joints of the apparatus for gravel packing an interval of a wellbore of the present invention is substantially similar to mating typical joints of pipe to form a pipe string requiring no special coupling tools or techniques.

0052Sand control screen <b>154</b> includes outer wrapper <b>166</b> that has a plurality of openings <b>168</b>. Likewise, sand control screen <b>156</b> includes outer wrapper <b>170</b> that has a plurality of openings <b>172</b>. Sand control screen <b>154</b> has a pair of channels <b>174</b> and a pair of sheet members <b>176</b> attached thereto, only one of each being visible in <figref idref="DRAWINGS">FIG. 5</figref>. Channels <b>174</b> include outlets <b>178</b>. Likewise, sand control screen <b>156</b> has a pair of channels <b>180</b> and a pair of sheet members <b>182</b> attached thereto. Channels <b>180</b> includes a plurality of outlets <b>184</b> which are not visible in <figref idref="DRAWINGS">FIG. 5</figref>. In the illustrated embodiment, sand control screens <b>154</b>, <b>156</b> would be positioned within outer tubulars <b>150</b>, <b>152</b> such that outlets <b>178</b> are axially and circumferentially aligned with outlets <b>160</b> of outer tubular <b>150</b>, as best seen in <figref idref="DRAWINGS">FIG. 6</figref> and such that outlets <b>184</b> are axially and circumferentially aligned with outlets <b>164</b> of outer tubular <b>152</b>, as best seen in <figref idref="DRAWINGS">FIG. 7</figref>.

0053Each joint of the apparatus of the present invention includes a pair of axially spaced apart substantially circumferential isolation members. For example, isolation members <b>186</b> are shown on sand control screen <b>154</b> in FIGS. <b>5</b> and <b>8</b>. Likewise, isolation members <b>188</b> are shown on sand control screen <b>156</b> in <figref idref="DRAWINGS">FIGS. 5 and 9</figref>.

0054Channels <b>174</b> define the circumferential boundaries of production pathways <b>188</b> and, together with sheet members <b>176</b>, channels <b>174</b> define slurry passageways <b>190</b>. Isolation members <b>186</b> help provide fluid isolation between production pathways <b>188</b> and slurry passageways <b>190</b>. Channels <b>180</b> define the circumferential boundaries of production pathways <b>192</b> and, together with sheet members <b>182</b>, channels <b>180</b> define slurry passageways <b>194</b>. Isolation members <b>188</b> help provide fluid isolation between production pathways <b>192</b> and slurry passageways <b>194</b>.

0055Importantly, however, slurry passageways <b>190</b> and slurry passageways <b>194</b> are all in fluid communication with one another such that a fluid slurry may travel in and between these passageways from one joint of the apparatus for gravel packing an interval of a wellbore of the present invention to the next. Specifically, as best seen in <figref idref="DRAWINGS">FIGS. 4 and 5</figref>, an annular region <b>196</b> exists between outer tubulars <b>150</b>, <b>152</b> and sand control screens <b>154</b>, <b>156</b> that allows the fluid slurry to travel downwardly from slurry passageways <b>190</b> through annular region <b>196</b> into slurry passageways <b>194</b>. As such, regardless of the circumferential orientation of sand control screen <b>154</b> relative to sand control screen <b>156</b>, the fluid slurry will travel down through each joint of the apparatus for gravel packing an interval of a wellbore of the present invention.

0056It should be apparent to those skilled in the art that the use of directional terms such as above, below, upper, lower, upward, downward and the like are used in relation to the illustrative embodiments as they are depicted in the figures, the upward direction being toward the top of the corresponding figure and the downward direction being toward the bottom of the corresponding figure. It should be noted, however, that the apparatus for gravel packing an interval of a wellbore is not limited to such orientation as it is equally-well suited for use in inclined and horizontal orientations.

0057As should be apparent to those skilled in the art, the apparatus for gravel packing an interval of a wellbore of the present invention may have a variety of configurations including configurations having other numbers of slurry passageways such as one, three, four or more slurry passageways, such configurations being considered within the scope of the present invention.

0058Referring next to <figref idref="DRAWINGS">FIGS. 10 and 11</figref>, therein are depicted a portion of a joint of the gravel packing apparatus of the present invention with the outer tubular removed wherein two screen sections are attached to the single joint of base pipe. Screen sections <b>200</b> and <b>202</b> are each attached to a single joint of base pipe <b>204</b>. In the illustrated embodiment, screen section <b>200</b> includes a screen wrapper <b>206</b> and a filter medium <b>208</b>. Likewise, screen section <b>202</b> includes a screen wrapper <b>212</b> and a filter medium <b>214</b>.

0059As screen sections <b>200</b>, <b>202</b> are commonly shorter than base pipe <b>204</b>, two or more screen sections are preferably attached to each base pipe joint. This may be achieved by sliding screen sections <b>200</b>, <b>202</b> onto base pipe <b>204</b> with a spacer member <b>218</b> positioned therebetween. In the illustrated embodiment, spacer member <b>218</b> is an annular ring having a two tier radial surface configuration that provides support to the respective ends of screen members <b>200</b>, <b>202</b> which are secured to spacer member <b>218</b> by welding or other suitable technique. The other ends of screen sections <b>200</b>, <b>202</b> are attached to base pipe <b>204</b> in a similar manner if additional screen sections are adjacent to the other ends of screen sections <b>200</b>, <b>202</b>. Alternatively, if screen sections <b>200</b>, <b>202</b> are the last screen sections at the ends of base pipe <b>204</b>, a simple ring or an isolation member, such as isolation member <b>188</b> of <figref idref="DRAWINGS">FIG. 9</figref>, may be used to attach the other ends of screen sections <b>200</b>, <b>202</b> to base pipe <b>204</b>.

0060Either before or after screen sections <b>200</b>, <b>202</b> have been attached to base pipe <b>204</b>, respective sheet members <b>220</b>, <b>222</b> and channels sections <b>224</b>, <b>226</b> are attached to screen sections <b>200</b>, <b>202</b> by welding or other suitable technique. As a gap exists between channels sections <b>224</b>, <b>226</b> in this configuration, a channel segment <b>228</b> is attached to the adjacent exposed ends of channels sections <b>224</b>, <b>226</b> such that a continuous slurry passageway <b>230</b> is formed that extends substantially the entire length of the joint of the gravel packing apparatus of the present invention.

0061Instead of using an annular ring having a two tier radial surface configuration as the spacer member, a spacer member <b>240</b> that comprises an annular ring having a single radial surface configuration could alternatively be used, as best seen in <figref idref="DRAWINGS">FIG. 12</figref>. In this embodiment, a pad <b>242</b> having approximately the same circumferential width as the channel may be used. Pad <b>242</b> is attached to spacer member <b>240</b> by welding or other suitable technique. The remaining assembly of the joint of the gravel packing apparatus of the present invention is substantially the same as that described with reference to <figref idref="DRAWINGS">FIGS. 10 and 11</figref>.

0062Referring next to <figref idref="DRAWINGS">FIG. 13</figref>, therein is depicted another embodiment of spacer member that is designated <b>250</b>. In this embodiment, spacer member <b>250</b> is an annular ring having a single radial surface configuration. The remaining assembly of the joint of the gravel packing apparatus of the present invention is substantially the same as that described with reference to <figref idref="DRAWINGS">FIGS. 10 and 11</figref> except that a channel segment <b>252</b> is attached to spacer member <b>250</b> without the aid of a raised center section or a pad by welding or other suitable technique to complete slurry passageway <b>230</b>.

0063Referring now to <figref idref="DRAWINGS">FIG. 14</figref>, a typical completion process using an apparatus <b>300</b> for gravel packing an interval of a wellbore of the present invention will be described. First, interval <b>48</b> adjacent to formation <b>14</b> is isolated. Packer <b>44</b> seals the upper end of annular interval <b>48</b> and packer <b>46</b> seals the lower end of annular interval <b>48</b>. Cross-over assembly <b>302</b> is located adjacent to screen assembly <b>304</b>, traversing packer <b>44</b> with portions of cross-over assembly <b>302</b> on either side of packer <b>44</b>. When the gravel packing operation commences, the objective is to uniformly and completely fill interval <b>48</b> with gravel. To help achieve this result, wash pipe <b>306</b> is disposed within screen assembly <b>304</b>. Wash pipe <b>306</b> extends into cross-over assembly <b>302</b> such that return fluid passing through screen assembly <b>304</b>, indicated by arrows <b>308</b>, may travel through wash pipe <b>306</b>, as indicated by arrow <b>310</b>, and into annulus <b>52</b>, as indicted by arrow <b>312</b>, for return to the surface.

0064The fluid slurry containing gravel is pumped down work string <b>30</b> into cross-over assembly <b>302</b> along the path indicated by arrows <b>314</b>. The fluid slurry containing gravel exits cross-over assembly <b>302</b> through cross-over ports <b>316</b> and is discharged into apparatus <b>300</b> as indicated by arrows <b>318</b>. In the illustrated embodiment, the fluid slurry containing gravel then travels between channels <b>320</b> and sheet member <b>322</b> as indicated by arrows <b>324</b>. At this point, portions of the fluid slurry containing gravel exit apparatus <b>300</b> through outlets <b>326</b> of channels <b>320</b> and outlets <b>328</b> of outer tubular <b>330</b>, as indicated by arrows <b>332</b>. As the fluid slurry containing gravel enters annular interval <b>48</b>, the gravel drops out of the slurry and builds up from formation <b>14</b>, filling perforations <b>50</b> and annular interval <b>48</b> around apparatus <b>300</b> forming the gravel pack. Some of the carrier fluid in the slurry may leak off through perforations <b>50</b> into formation <b>14</b> while the remainder of the carrier fluid passes through screen assembly <b>304</b>, as indicated by arrows <b>308</b>, that is sized to prevent gravel from flowing therethrough. The fluid flowing back through screen assembly <b>304</b>, as explained above, follows the paths indicated by arrows <b>310</b>, <b>312</b> back to the surface.

0065In operation, the apparatus for gravel packing an interval of a wellbore of the present invention is used to distribute the fluid slurry to various locations within the interval to be gravel packed by injecting the fluid slurry into the slurry passageways created by the channels and the sheet members of one or more joints of the apparatus. The fluid slurry exits through the various outlets along the slurry passageway and enters the annulus between the apparatus and the wellbore which may be cased or uncased. Once in this annulus, a portion of the gravel in the fluid slurry is deposited around the apparatus in the annulus such that the gravel migrates both circumferentially and axially from the outlets. This process progresses along the entire length of the apparatus such that the annular area becomes completely packed with the gravel. In addition, a portion of the fluid slurry enters the opening of the outer tubular which provides for the deposit of a portion of the gravel from the fluid slurry in the production pathways between the outer tubulars and the sand control screens. Again, this process progresses along the entire length of the apparatus such that each production pathway becomes completely packed with the gravel. Once both the annulus and the production pathways are completely packed with gravel, the gravel pack operation may cease.

0066In some embodiments of the present invention, the fluid slurry may not initially be injected into the slurry passageways. Instead, the fluid slurry is injected directly into the annulus between the apparatus <b>340</b> and the wellbore, as best seen in <figref idref="DRAWINGS">FIG. 15</figref>. In the illustrated embodiment, the primary path for the fluid slurry containing gravel as it is discharged from exit ports <b>316</b>, is directly into annular interval <b>48</b> as indicated by arrows <b>334</b>. This is the primary path as the fluid slurry seeks the path of least resistance. Under ideal conditions, the fluid slurry travels throughout the entire interval <b>48</b> until interval <b>48</b> is completely packed with gravel. In addition, the fluid slurry enters the production pathways of apparatus <b>340</b> such that this area is also completely packed with gravel.

0067It has been found, however, that sand bridges commonly form during the gravel packing of an interval when the fluid slurry is pumped directly into annular interval <b>48</b>. These sand bridges are bypassed using the apparatus for gravel packing an interval of a wellbore of the present invention by first allowing the fluid slurry to pass through the outer tubular into the production pathways of apparatus <b>340</b>, bypassing the sand bridge and then returning to annular interval <b>48</b> through the outer tubular to complete the gravel packing process. These pathways are considered the secondary path for the fluid slurry. If a sand bridge forms in the secondary paths prior to completing the gravel packing operation, then the fluid slurry enters channels <b>320</b> as indicated by arrows <b>318</b> and as described above with reference to <figref idref="DRAWINGS">FIG. 14</figref>. In this embodiment, channels <b>320</b> are considered the tertiary path for the fluid slurry.

0068In either embodiment, once the gravel pack is completed and the well is brought on line, formation fluids that are produced into the gravel packed interval must travel through the gravel pack in the annulus, then enter the production pathways through the openings in the outer tubular where the formation fluids pass through the gravel pack between the outer tubular and the screen assembly. As such, the apparatus for gravel packing an interval of a wellbore of the present invention allows for a complete gravel pack of an interval so that particulate materials in the formation fluid are filtered out.

0069While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.