Method for gravel packing geothermal well
By using reverse circulation pumps to inject sand-carrying fluid and employing packers for sealing, the problem of sand production during directional well formation has been solved, achieving effective sand control for geothermal wells, especially those with an inclination angle greater than 10°, thus improving production efficiency and well stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2024-11-21
- Publication Date
- 2026-05-22
AI Technical Summary
Existing technologies have problems with sand plugging and poor sand control in directional well construction, especially in geothermal wells with an inclination angle greater than 10°. Artificial gravel filling is difficult to effectively fill the production section, leading to sand bridge formation and affecting the normal production of the well.
A surface pump truck is used to pump sand-carrying fluid through reverse circulation, carrying sand-blocking gravel to the bottom of the well. A packer is then used to set the annulus, dividing it into upper and lower parts. The aperture of the sand-blocking screen and the particle size of the sand-blocking gravel are determined according to the size of the formation sand. Clay balls are then filled to cover the upper part of the sand-blocking gravel to enhance the sealing effect.
It effectively blocks formation sand, prevents sand bridge formation, improves the sand control effect of geothermal wells, ensures the quality of geothermal water, enhances the rigidity and stability of the setting position, and solves the problem of difficult sand blockage during directional well construction.
Smart Images
Figure CN122071922A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of geothermal reservoir development technology, and in particular to a method for geothermal well formation using dynamic water-filled gravel. Background Technology
[0002] Sandstone geothermal reservoirs with high levels of underground thermal energy development and utilization are mostly located in Neogene or Paleogene strata. These strata are loosely cemented and prone to sand production, which is one of the important problems affecting the development of sandstone geothermal reservoirs. Sand production in geothermal wells can lead to reduced or stopped production, accelerated corrosion of surface pipelines and downhole equipment, damage or rupture of casing in the well, and even the abandonment of the geothermal well. At present, relatively mature sand control technology has been developed for vertical wells, but for directional wells, problems such as difficulty in plugging sand production and poor sand control effect still exist. Summary of the Invention
[0003] In view of the above problems, the purpose of this invention is to provide a method for geothermal well filling with gravel and dynamic water.
[0004] This invention provides a method for geothermal well construction using gravel filling with dynamic water flow, comprising:
[0005] After the geothermal well is completed and logged, the entire well section tubing is run in one go. The entire well section tubing includes: connecting drill pipe, release connector and completion tubing connected from top to bottom.
[0006] A reverse circulation pump injects a sand-carrying fluid into the annulus formed by the entire well section tubing and the geothermal wellbore. Pumping is stopped once the reverse circulation gravel-filling pump pressure rises to a preset pressure. The sand-carrying fluid contains sand-blocking gravel.
[0007] The connecting drill pipe is pulled out, and the return pipe string is lowered in to connect with the completion string. A packer is used to seal the connection point, dividing the annulus into an upper annulus and a lower annulus.
[0008] In one embodiment, the completion string includes, from top to bottom, a connecting casing, a sand-blocking screen, a sedimentation pipe, and a plug.
[0009] In one embodiment, the aperture of the sand-blocking screen is smaller than the particle size of the formation sand;
[0010] The median particle size of the sand-blocking gravel is taken as 5-6 times the median particle size of the formation sand.
[0011] In one embodiment, the above-described geothermal well water-filled gravel well formation method further includes:
[0012] After the step of setting the seal using a sealing tool, the airtightness at the setting location is checked.
[0013] In one embodiment, detecting the airtightness at the sealing position includes:
[0014] A pressure test is conducted by pressurizing the upper annulus with a preset amount of water. If the pressure stabilization time is greater than or equal to 30 minutes, the airtightness is qualified; if the pressure stabilization time is less than 30 minutes, the airtightness is unqualified.
[0015] In one embodiment, detecting the airtightness at the sealing position further includes:
[0016] If the sealing performance at the sealing position is not up to standard, replace the sealing tool, re-seal with the new sealing tool, and test the sealing performance of the new sealing tool until the sealing performance is up to standard.
[0017] In one embodiment, the above-described geothermal well water-filled gravel well formation method further includes:
[0018] Before the step of running the entire well section of tubing in one go, the first and second drilling operations are performed.
[0019] In one embodiment, it also includes:
[0020] After the reverse circulation pumping step of injecting sand-carrying fluid and before the setting with a sealing tool, clay balls are filled into the annulus.
[0021] In one embodiment, the initial drilling includes:
[0022] Within the initial drilling depth range, cementing casing is installed, and cementing operations are carried out.
[0023] In one embodiment, the top depth of the connecting casing is less than the bottom depth of the cementing casing.
[0024] In one embodiment, the above-described geothermal well water-filled gravel well formation method further includes:
[0025] After the step of running the entire well section tubing in one go and before the step of pumping sand-carrying fluid in reverse circulation, the construction surface pressure is determined.
[0026] In one embodiment, the above-described geothermal well water-filled gravel well formation method further includes:
[0027] After the step of setting the geothermal well using a packer, well washing and handover operations are performed.
[0028] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:
[0029] This invention provides a method for geothermal well construction using dynamic water gravel filling. A surface pump truck injects a sand-carrying fluid containing sand-blocking gravel into the bottom of the geothermal well. This solves the problem of sand bridges caused by gravel accumulation and sedimentation in the inclined section of geothermal wells with an inclination angle greater than 10°, which prevents effective filling of the production section. After pumping in the sand-carrying fluid, a packer is used for sealing, further preventing a small amount of formation sand passing through the sand-blocking gravel from contaminating the geothermal water within the lower annulus.
[0030] Furthermore, the aperture of the sand-blocking screen and the particle size of the sand-blocking gravel are determined according to the size of the formation sand, which increases the targeting and effectiveness.
[0031] Furthermore, soil balls are filled into the annulus to cover the top of the sand-blocking gravel, which serves to block a small amount of stratum sand.
[0032] Furthermore, after drilling begins, cementing casing is run in for cementing. The top depth of the connecting casing in the entire well section is less than the bottom depth of the cementing casing. This enhances the rigidity, stability, and strength of the setting position when using packers for setting, resulting in a better sealing effect.
[0033] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0034] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:
[0035] Figure 1 This is a flowchart of a geothermal well gravel filling method according to an embodiment of the present invention;
[0036] Figure 2 This is a schematic diagram of drilling in one embodiment of the present invention;
[0037] Figure 3 This is a schematic diagram of a cementing operation in one embodiment of the present invention;
[0038] Figure 4 This is a schematic diagram of the second drilling operation in an embodiment of the present invention;
[0039] Figure 5 This is a schematic diagram of the entire well section tubing being run in an embodiment of the present invention;
[0040] Figure 6 This is a schematic diagram of reverse circulation pumping for gravel filling in an embodiment of the present invention;
[0041] Figure 7 This is a schematic diagram of filling clay balls in an embodiment of the present invention;
[0042] Figure 8 This is a schematic diagram of the drill rod being pulled out in an embodiment of the present invention;
[0043] Figure 9 This is a schematic diagram of the sealing tool used in an embodiment of the present invention;
[0044] Figure 10 This is a schematic diagram of the retraction pipe column in an embodiment of the present invention. Detailed Implementation
[0045] This invention provides a method for geothermal well construction using dynamic water gravel filling. Although exemplary embodiments of this disclosure are shown in the accompanying drawings, it should be understood that this disclosure can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this disclosure and to fully convey the scope of this disclosure to those skilled in the art.
[0046] This invention provides a method for geothermal well construction using dynamic water gravel filling, referring to... Figure 1 As shown, the method includes the following steps:
[0047] S11. After the geothermal well is completed and logged, the entire well section tubing is run in one go. The entire well section tubing includes: connecting drill pipe, release connector and completion tubing connected from top to bottom.
[0048] S12. Inject sand-carrying fluid into the annulus formed by the entire well section tubing and the geothermal wellbore through reverse circulation pumping. Stop pumping when the reverse circulation gravel-filling pump pressure rises to the preset pressure. The sand-carrying fluid contains sand-blocking gravel.
[0049] S13. Remove the connecting drill pipe, lower the return pipe string and connect it to the completion string, and use a packer to seal the connection point, dividing the annulus into an upper annulus and a lower annulus.
[0050] This invention provides a method for geothermal well completion using dynamic water-filled gravel, with main steps including S11, running the entire well section tubing; S12, reverse circulation pumping of sand-carrying fluid; and S13, setting the well using a packer. After well completion and logging, the entire well section tubing is run in one go, with the lower part connected to the completion tubing. A surface pump truck continuously pumps sand-carrying fluid into the wellbore and the annulus formed by the entire well section tubing. The sand-blocking gravel in the sand-carrying fluid gradually accumulates upwards from the bottom of the geothermal well within the annulus, preventing formation sand from gushing out. After the reverse circulation gravel filling reaches the preset conditions, the connecting drill pipe at the top of the entire well section tubing is retrieved, and a return tubing is run and connected to the lower completion tubing. A packer is used at the connection point to set the well, further isolating the formation sand.
[0051] Step S11 mainly involves running the entire well section tubing string at once. The entire well section tubing string includes connecting drill pipe, release connector, and completion tubing string.
[0052] In one embodiment, the completion string includes, from top to bottom, a connecting casing, a sand-blocking screen, a settling pipe, and a plug. Therefore, during the process of running the entire well section of the string into a geothermal well, the following components are run in sequence: plug, settling pipe, sand-blocking screen, connecting casing, release connector, and connecting drill pipe.
[0053] In one embodiment, the aperture of the sand-blocking screen is smaller than the particle size of the formation sand. The aperture of the sand-blocking screen can be selected according to the particle size or diameter of the formation sand under actual working conditions.
[0054] Before step S11, i.e., before the step of running the entire well section tubing in one go, in one embodiment, pre-set drill bits of different sizes are used to perform initial drilling and second drilling operations. For example, after drilling to the first design depth using the first pre-set drill bit, the first drilling string is pulled out; after drilling to the second design depth (i.e., the geothermal well design depth) using the second pre-set drill bit, the corresponding drilling string (second drilling string) is pulled out.
[0055] In one embodiment, after drilling to the first designed depth and retrieving the first drill string, and before proceeding with the second drilling, cementing casing is run within the first drilling depth range, and cementing operations are performed. This serves two purposes: firstly, to seal the unstable formation within the first drilling depth range, creating conditions for the next step of the second drilling; and secondly, to provide favorable conditions for the subsequent step S13, which uses a packer tool for setting.
[0056] In one embodiment, the depth of the top end of the completion casing in step S11 is less than the depth of the bottom end of the cementing casing. This creates conditions for setting the casing using a packer in the subsequent step S13 to achieve a good packing effect.
[0057] Step S12 mainly involves reverse circulation gravel packing. Sand-carrying fluid is pumped from a surface pump truck into the annulus formed between the entire wellbore tubing and the geothermal wellbore. Specifically, the annulus includes the cementing casing within the upper part of the first drilling depth range, forming annulus with the connecting drill pipe in the upper part of the entire wellbore tubing, and the geothermal wellbore within the lower part of the second drilling depth range, forming annulus with the completion tubing in the lower part of the entire wellbore tubing.
[0058] In one embodiment, the particle size of the sediment-retaining gravel in the sediment-carrying fluid can be determined according to the Société formula, for example, the median particle size of the sediment-retaining gravel can be taken as 5-6 times the median particle size of the formation sand. The particle size / diameter of the sediment-retaining gravel can be selected based on the particle size / diameter of the formation sand in the actual working conditions.
[0059] In one embodiment, before proceeding to step S12, the construction surface pressure is determined to avoid fracturing the formation during the pumping of the sand-carrying fluid. The construction surface pressure is the maximum pumping pressure, and the discharge rate of the sand-carrying fluid in the reverse circulation gravel filling is controlled based on the calculated construction surface pressure.
[0060] The ground pressure during construction is calculated using the following formula:
[0061] P 地面 =P 破裂 -P 液柱 +P 摩阻 ;
[0062] in:
[0063] P 地面 : Construction ground pressure, MPa;
[0064] P 破裂 Formation fracture pressure, MPa;
[0065] P 液柱 : Liquid column pressure, MPa;
[0066] P 摩阻 Construction friction pressure, MPa.
[0067] In one embodiment, the reverse circulation gravel filling pump pressure is monitored. Reverse circulation gravel filling stops when the surface pump pressure rises to a preset pressure. This preset pressure corresponds to the surface pump pressure at which the upper depth of the sand-blocking gravel accumulated in the annulus is approximately level with the upper depth of the sand-blocking screen in the completion string. At this point, the gravel filling work has met the preset requirements. Under the combined action of the sand-blocking gravel and the sand-blocking screen, most of the formation sand can be blocked. After reverse circulation gravel filling is completed, clay balls are filled into the annulus, covering the top of the sand-blocking gravel, which can block a small portion of the formation sand that has penetrated the sand-blocking gravel beneath the clay balls.
[0068] Step S13 involves using a sealing tool to create a seal, thereby dividing the annulus into an upper annulus and a lower annulus at the docking point. By sealing the annulus, even if a small amount of formation sand, gravel, or clay balls seep out, the sealing device will contain them within the lower annulus, preventing contamination of the geothermal water.
[0069] In one embodiment, after sealing with a packer tool, the airtightness at the sealing location is tested.
[0070] In one embodiment, a preset amount of water is pressured into the upper annulus above the geothermal wellhead for a pressure test. If the pressure stabilization time is greater than or equal to 30 minutes, the tightness is qualified; if the pressure stabilization time is less than 30 minutes, the tightness is unqualified. For example, according to the actual working conditions, pump a preset amount of water into the upper annulus and observe the liquid level change in the upper annulus. If the liquid level does not change or the liquid level height change is below a preset value within 30 minutes, it indicates that the tightness is qualified; otherwise, it indicates that the tightness is unqualified.
[0071] In one embodiment, if the tightness at the setting position is unqualified, replace the packer tool, re-set the packer with a new packer tool, and detect the tightness of the new packer tool until the tightness test is qualified.
[0072] In one embodiment, after setting the packer with the packer tool, pull out the return string.
[0073] In one embodiment, after setting the packer with the packer tool, perform a well flushing operation and a well handover operation on the geothermal well. For example, use an air compressor to flush the geothermal well until the sand content in the geothermal water in the geothermal well is less than 1 / 10000; install a special wellhead for the geothermal well to complete the well handover work.
[0074] The embodiment of the present invention provides a method for forming a geothermal well with gravel filling under flowing water. First, perform the first-stage drilling. After the first-stage drilling is completed and the well is formed, lower the cementing casing for cementing to seal the loose surface formation. Then perform the second-stage drilling. After the second-stage drilling is completed, perform well logging, lower the full well section string, and successively lower the plug, sedimentation pipe, sand screen pipe, connecting casing, releasing joint, and connecting drill pipe according to the pipe laying sequence. The part below the releasing joint is called the completion string.
[0075] Then, by controlling the displacement and pressure of the surface pump truck, on the premise of not fracturing the formation, reverse circulation pump the sand-carrying fluid from the annulus formed by the geothermal wellbore and the full well section string. After the sand-carrying fluid reaches the bottom of the geothermal well, the gravel gradually deposits at the bottom of the well and is blocked outside the sand screen pipe. Only the pure liquid in the sand-carrying fluid can pass through the sand screen pipe and enter the completion string, and then flow upward through the connecting drill pipe and return to the ground. When the surface pump pressure rises to the preset pressure, confirm that the gravel just covers the top depth position of the sand screen pipe, fill the annulus with clay balls. After filling, rotate the connecting drill pipe clockwise to unscrew and release, leave the completion string in the wellbore, lower the return string to dock with the completion string, press down the return string, set the packer tool, and divide the annulus into an upper annulus and a lower annulus to achieve the closure of the lower annulus.
[0076] Next, taking an actually developed geothermal well as an example, the construction process of gravel filling under flowing water will be described in detail.
[0077] (1) First-stage drilling: Refer to Figure 2The first pre-set drill bit with a diameter of φ444.5mm is used for the first drilling. After drilling to the first design depth, the corresponding first drilling string is pulled out.
[0078] (2) Cementing: Refer to Figure 3 A φ339.7mm cementing casing was lowered to the first design depth, and cementing was carried out in the first stage of cementing to seal the unstable formations within the first drilling depth range, creating conditions for the next stage of drilling.
[0079] (3) Second drilling: Refer to Figure 4 As shown, a second preset drill bit with a diameter of φ311.2mm is used for the second drilling operation. The drilling stops after reaching the second design depth, which is the design depth of the geothermal well, and the second drilling string used for the second drilling operation is pulled out.
[0080] (4) Run the entire well section tubing string: Refer to Figure 5 As shown, after the first and second drilling operations and the completion of the corresponding logging work, the entire well section of tubing is run in one go. Following the tubing sequence, the plug, sedimentation pipe, φ177.8mm sand screen pipe, φ177.8mm connecting casing, drop-off connector, and φ127mm connecting drill pipe are run in sequence.
[0081] (5) Determine the construction ground pressure: based on P 地面 =P 破裂 -P 液柱 +P 摩阻 The formula is used to calculate and determine the ground pressure during construction to prevent excessive pumping pressure from fracturing the formation during construction.
[0082] (6) Reverse circulation pump injection of sand-carrying fluid: Refer to Figure 6 As shown, the pumping rate of the sand-carrying fluid is controlled, and the fluid is injected into the annulus formed by the φ339.7mm cementing casing and the φ127mm connecting drill pipe, as well as the annulus formed by the φ311mm geothermal wellbore and the φ177.8mm connecting casing. The size of the sand-blocking gravel is determined according to the Sosi formula, i.e., the median particle size of the sand-blocking gravel is 5-6 times the median particle size of the formation sand. Pumping is stopped when the surface pump truck reaches the preset pressure value, which is the pumping pressure corresponding to the depth at which the pumped sand-blocking gravel just overflows the upper end of the sand-blocking screen in the completion string. The pumped sand-blocking gravel is blocked outside the sand-blocking screen, and the remaining sand-carrying fluid enters the completion casing through the sand-blocking screen and is then expelled to the surface through the connecting drill pipe.
[0083] (7) Fill in the clay ball: Refer to Figure 7 As shown, after the reverse circulation pumping of sand-carrying fluid is completed, 3-5mm clay balls are filled into the annulus to cover the top of the sand-blocking gravel.
[0084] (8) Drill pipe disconnection: Refer to Figure 8 As shown, the connecting drill pipe is rotated forward and then reversed and released, and the upper part of the connecting drill pipe in the entire well section is pulled out, leaving the lower part of the completion string inside the geothermal well.
[0085] (9) Seat cover: Refer to Figure 9 As shown, a φ127mm return pipe string is driven into the geothermal well and connected to the completion pipe string. After connection, the return pipe string is pressed down, and a packer is used for setting. The packer includes, for example, a return sealing assembly in the annulus and a plug at the junction of the return pipe string and the connecting casing. The packer divides the annulus into an upper annulus and a lower annulus.
[0086] (10) Pressure test: Pressurize the geothermal wellhead with 3MPa of water into the upper annulus for a pressure test. The standard for passing the pressure test is that the pressure stabilization time reaches 30 minutes or more. If the pressure test fails, replace the packer and re-set the packer. Then test the sealing performance of the new packer until the sealing performance is qualified.
[0087] (11) Remove the return pipe column. (Refer to...) Figure 10 As shown, the return pipe string is pulled out from the geothermal well.
[0088] (12) Well washing: Use an air compressor to wash the geothermal well until the water is clear and the sand is gone. The standard is that the sand content of the geothermal water is <1 / 10000.
[0089] (13) Well handover: Install the special wellhead for geothermal wells and complete the well handover operation.
[0090] The geothermal well filling method with dynamic water provided in this invention provides a superior sand control and retention effect compared to previous geothermal well development methods that suffered from poor sand control. Especially for directional geothermal wells with an inclination angle greater than 10°, reverse circulation gravel filling using a surface pump truck allows the sand-carrying fluid to flow smoothly within the annulus. After the gravel fills the bottom of the well, the pure liquid in the sand-carrying fluid returns to the surface through the completion tubing. Furthermore, setting the well after pumping the sand-carrying fluid further completely retains any small amount of formation sand passing through the retaining gravel within the lower annulus. This invention effectively solves the problem of sand bridges appearing in artificially filled gravel formations when the inclination angle of a directional geothermal well is greater than 10°, preventing effective filling of the production well section, and provides a solution for sand control in geothermal wells with inclination angles greater than 10°.
[0091] Obviously, those skilled in the art can make various modifications to this invention without departing from its spirit and scope. Therefore, if these modifications fall within the scope of the claims and their equivalents, this invention is also intended to include these modifications.
Claims
1. A method for geothermal well formation using dynamic water and gravel filling, characterized in that, include: After the geothermal well is completed and logged, the entire well section tubing is run in one go. The entire well section tubing includes: connecting drill pipe, release connector and completion tubing connected from top to bottom. A reverse circulation pump injects a sand-carrying fluid into the annulus formed by the entire well section tubing and the geothermal wellbore. Pumping is stopped once the reverse circulation gravel-filling pump pressure rises to a preset pressure. The sand-carrying fluid contains sand-blocking gravel. The connecting drill pipe is pulled out, and the return pipe string is lowered in to connect with the completion string. A packer is used to seal the connection point, dividing the annulus into an upper annulus and a lower annulus.
2. The well-forming method as described in claim 1, characterized in that, The well completion string includes, from top to bottom, a connecting casing, a sand screen, a sedimentation pipe, and a plug.
3. The well-forming method as described in claim 2, characterized in that, The aperture of the sand-blocking screen is smaller than the particle size of the formation sand; The median particle size of the sand-blocking gravel is taken as 5-6 times the median particle size of the formation sand.
4. The well-forming method as described in claim 3, characterized in that, Also includes: After the step of setting the seal using a sealing tool, the airtightness at the setting location is checked.
5. The well-forming method as described in claim 4, characterized in that, The test of the airtightness at the sealing position includes: A pressure test is conducted by pressurizing the upper annulus with a preset amount of water. If the pressure stabilization time is greater than or equal to 30 minutes, the airtightness is qualified; if the pressure stabilization time is less than 30 minutes, the airtightness is unqualified.
6. The well-forming method as described in claim 5, characterized in that, The method of detecting the airtightness at the sealing position also includes: If the sealing performance at the sealing position is not up to standard, replace the sealing tool, re-seal with the new sealing tool, and test the sealing performance of the new sealing tool until the sealing performance is up to standard.
7. The well-forming method as described in claim 6, characterized in that, Also includes: Before the step of running the entire well section of tubing in one go, the first and second drilling operations are performed.
8. The well-forming method as described in claim 7, characterized in that, Also includes: After the reverse circulation pumping step of injecting sand-carrying fluid and before the setting with a sealing tool, clay balls are filled into the annulus.
9. The well-forming method as described in claim 8, characterized in that, The aforementioned drilling operation includes: Within the initial drilling depth range, cementing casing is installed, and cementing operations are carried out.
10. The well-forming method as described in claim 9, characterized in that, The depth of the top end of the connecting casing is less than the depth of the bottom end of the cementing casing.
11. The well-forming method according to any one of claims 1-10, characterized in that, Also includes: After the step of running the entire well section tubing in one go and before the step of pumping sand-carrying fluid in reverse circulation, the construction surface pressure is determined.
12. The well-forming method according to any one of claims 11, characterized in that, Also includes: After the step of setting the geothermal well using a packer, well washing and handover operations are performed.