A method for controlling water and draining sand in horizontal wells

Abstract

The present invention discloses a method for controlling water and draining sand in horizontal wells, the method comprising: utilizing cyclone sedimentation and cation aggregation to control water and drain sand for the fluid flowing into the screen pipe; the fluid comprises water and mud and sand. The present invention innovatively utilizes cyclone sedimentation and cation aggregation to control the water and mud and sand flowing into the screen pipe, and controls the more difficult water and sand in different time periods and layers, thereby achieving control of gas, water, and sand in different mining cycles, reasonably adjusting the edge and bottom water height, and adjusting the production profile of the horizontal well in real time, achieving full-life water and sand production control with mid-term flow control and late-stage sand drainage, ensuring smooth gas production channels in the near-well zone, maximizing mining production capacity, and ensuring a stable production cycle.

Description

Technical Field

[0001] The present invention relates to hydrate and high-mud gas well mining technology, and in particular to a horizontal well water control and sand removal method. Background Art

[0002] During the production of hydrates and high-mud content gas wells, pore water migration can easily cause sand production in the formation, even connecting to the aquifer. This can lead to massive water and sand production in the wellbore within a short period of time, burying the wellbore. Currently, there are no water control and sand removal methods for hydrate production and gas resource extraction in high-mud content sand layers. Existing water control technologies in oil and gas reservoirs and coalbed methane (CBM) are mostly used to address complex situations such as flooding and water inrush during oil well production. These technologies involve the development of oil-repellent and water-control devices, or, in CBM, the direct insertion of segmented packers and cementing to seal water.

[0003] Water control devices, cementing to seal water, or methods like exploiting differences in oil and water properties to control water and produce oil all share a common characteristic: they are water control designs developed for specific oil production areas. However, the extraction of natural gas hydrates and other muddy and water-bearing gas reservoirs does not involve oil layers. The materials entering the wellbore include formation mud and sand, formation water, decomposed natural gas hydrate gas, and a small amount of construction debris. Therefore, it is impossible to design water control mechanisms based on the difference in oil-water viscosity coefficients, and existing reservoir water control methods are not applicable to the development of these resources. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a method for controlling water and draining sand in a horizontal well to achieve the purpose of controlling water and draining sand.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] A method for controlling water and draining sand in a horizontal well, comprising:

[0007] The fluid flowing into the screen tube is subjected to cyclonic sand settling and cation aggregation to achieve the purpose of water control and sand removal; the fluid includes water and mud and sand.

[0008] Furthermore, the cyclone sand settling method includes: gathering the water and mud and sand flowing into the screen tube into a spiral tube.

[0009] Furthermore, the cation aggregation method includes: water control and sand removal devices are arranged at intervals in the length direction of the spiral tube, and the water control and sand removal devices include two cation aggregation plates, which are arranged opposite to each other. When the cation aggregation plates are energized, the anions are grounded and dissipated, and the cations are gathered on the cation aggregation plates to adsorb the mud and sand flowing through the spiral tube.

[0010] Furthermore, in the initial stage of mining, the cation aggregation plate is not energized, and the gas, water, mud and sand entering the screen pipe enter the wellbore through the production port of the screen pipe and are produced and collected on the ground.

[0011] Furthermore, in the middle stage of mining, when water control and sand removal operations are required, the cationic aggregation plate is energized, and the mud and sand flowing through the spiral tube are adsorbed and gradually gathered, and the water flow channel in the spiral tube will gradually decrease, and the water volume will decrease accordingly.

[0012] Furthermore, when the water volume decreases, the flow rate of the mud-containing liquid in the spiral tube decreases, and the mud and sand have sufficient time to undergo sedimentation reaction. The settled mud and sand will also reduce the flow space of the spiral sedimentator, thereby increasing the pressure of the produced water flow and achieving the purpose of water control.

[0013] Furthermore, in the later stage of mining, if the power supply of the cation aggregation plate is stopped or reduced, the cation aggregation plate loses or reduces its adsorption force on the mud and sand, and the mud and sand accumulated on the cation aggregation plate begin to decompose and move with the water flow. The production channel of the spiral tube is gradually released, the water flow increases, the liquid flow rate in the spiral tube increases, and the mud and sand are also carried into the wellbore. The water-bearing profile drives the gas reservoir around the wellbore into the wellbore.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention innovatively controls the water and mud and sand flowing into the screen pipe by using cyclonic sedimentation and cationic aggregation to control the more difficult water and sand in different time periods and layers, thereby achieving different mining cycles, controlling gas, water and sand, reasonably adjusting the edge and bottom water heights, and adjusting the production profile of the horizontal well in real time, realizing mid-term flow restriction and late-stage sand discharge control over water and sand production throughout the life cycle, ensuring smooth gas production channels near the wellbore, maximizing mining production capacity, and ensuring a stable production cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the operation and use of the horizontal well water control and sand removal method provided by an embodiment of the present invention;

[0017] Figure 2 for Figure 1 A local enlarged schematic diagram in FIG.

[0018] In the figure: 1, screen tube; 1-1, production port; 2, spiral tube; 3, cation aggregation plate; 100, formation; 200, casing. DETAILED DESCRIPTION

[0019] Example:

[0020] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0021] When developing high-mud-water gas and hydrate reservoirs, the casing 200 in the formation 100 provides a stable wellbore structure. Under conventional circumstances, the wellbore structure is a horizontal well extending horizontally. As the decomposed water from hydrates and gases carries produced water and sand from the formation into the near-wellbore zone, limited by the pore structure and sand drainage capacity, mud and sand form bridges and accumulate in the micropores, causing a combined water-sand blockage. This significantly reduces the gas permeability of the original channel and leads to a decrease in production capacity. Furthermore, during the hydrate decomposition process, the main substances entering the wellbore include methane gas, decomposed water, existing pore water, and formation mud and sand particles, with these three substances being the main components. Gas migration resistance is relatively low, and permeability requirements are relatively low. However, as mining progresses, the water production rates faced by different horizontal sections vary. If water control is not implemented, the pore structure around the wellbore will be flooded in a short period of time. The water-locking effect of the micropore structure is significant, affecting gas production.

[0022] Therefore, during different mining periods, water control and sand removal operations should be carried out in combination with the problem of side and bottom water ridge intrusion, so as to adjust the balance of the liquid production profile and extend the stable production period.

[0023] Because clay is primarily composed of silicates and carbonates, its particles are generally negatively charged. This is primarily due to: ① Isomorphous substitution within the clay lattice, whereby Si (tetravalent) is replaced by aluminum (trivalent) in some silicon-oxygen tetrahedra, and aluminum (trivalent) is replaced by magnesium or iron (divalent) in some aluminum-oxygen octahedra, resulting in residual negative charge. ② Negative charge can also be generated by the dissociation of carboxyl groups contained in some seafloor humus, releasing hydrogen atoms (H+). Once the hydrogen atoms on the carboxyl groups dissociate, they become negatively charged ions. ③ As pH changes, alkaline environments favor H+ dissociation to generate more negative charge. The pH of the pore water in the South China Sea hydrate reservoirs known to date is generally between 7 and 9, a weakly alkaline state, which favors clays exhibiting a strong negative charge, or anionic charge. Clay is easily attracted and aggregated by positive charges under the action of an external electric field, while reservoir water does not exhibit positive and negative charge adsorption characteristics. Therefore, the present invention will utilize the density and charge differences between water and clay to achieve the purpose of controlling water and draining sand. Based on this, the present invention innovatively controls the water and mud and sand flowing into the screen pipe 1 by using vortex sedimentation and cationic aggregation to control the more difficult water and sand in different time periods and layers, thereby achieving different mining cycles, controlling gas, water, and sand, reasonably adjusting the edge and bottom water height, and adjusting the production profile of the horizontal well in real time, achieving mid-term flow control and late-stage sand drainage for the entire life cycle of water and sand production, ensuring the smoothness of the gas production channel near the wellbore, maximizing mining production capacity, and ensuring a stable production cycle. The screen pipe 1 is sleeved in the casing 200.

[0024] In a specific embodiment, if Figure 1-2As shown, the above-mentioned cyclone sand settling method includes: converging the water and mud and sand flowing into the screen tube 1 into a spiral tube 2, and sorting the water and sand entering the spiral tube 2 in a spiral manner. Since the density of mud and sand is greater than that of water, when the flow rate is low, after the muddy water passes through the spiral tube 2, sand will form in the area with larger curvature, and water will be produced. Figure 1 The arrows shown in the figure are the flow directions of the fluids, which include gas, water and sand.

[0025] In one embodiment, the aforementioned cation aggregation method includes: a water control and sand removal device is arranged at intervals along the length of the spiral tube 2. The water control and sand removal device includes two cation aggregation plates 3, which are arranged opposite each other and are made of a single piece of metal. When the cation aggregation plates 3 are energized, the anions are grounded and dissipated, while the cations are accumulated on the cation aggregation plates 3, thereby adsorbing the mud and sand flowing through the spiral tube 2. In this way, when the cation aggregation plates stop releasing cations (no power is applied), the mud and sand lose their adhesion and are uniformly discharged from the wellbore. The flow rate within the spiral tube 2 is also increased, thereby discharging the sediment inside the spiral tube 2, achieving the purpose of slow or complete mud and sand discharge.

[0026] Therefore, in different periods of hydrate mining, the purpose of slow or complete discharge of mud and sand can be achieved by controlling whether the cation aggregation plate is energized.

[0027] In the initial stage of mining, the cation collecting plate 3 is not energized, and the gas, water, mud and sand entering the screen pipe 1 enter the wellbore through the production port 1-1 of the screen pipe 1 and are produced and collected on the ground.

[0028] In the middle stage of mining, the water production and sand production of different layers are judged based on production data. Some layers have serious bottom water ridges and there is a risk of flooding. The mud and sand transported to the vicinity of the wellbore begins to increase, and water control and sand removal operations are required. The cation aggregation plate 3 is energized, and the mud and sand flowing through the spiral tube 2 are adsorbed and gradually gathered. The water flow channel in the spiral tube 2 will gradually decrease, and the water volume will decrease accordingly. When the water volume decreases, the flow rate of the mud and sand liquid in the spiral tube 2 decreases, and the mud and sand have sufficient time to react with precipitation. The precipitated mud and sand will also reduce the flow space of the spiral tube 2, thereby increasing the pressure of the water production flow and achieving the purpose of water control.

[0029] In the later stage of mining, the power supply of the cation aggregation plate 3 is stopped or reduced, and the cation aggregation plate 3 loses or reduces its adsorption force on the mud and sand. The mud and sand accumulated on the cation aggregation plate 3 begin to decompose and move with the water flow. The production channel of the spiral tube 2 is gradually released, the water flow increases, the liquid flow rate in the spiral tube 2 increases, and the mud and sand are also carried into the wellbore. The water-bearing profile drives the gas reservoir around the wellbore into the wellbore.

[0030] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the essence of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for controlling water and draining sand in a horizontal well, characterized in that: The method comprises: The fluid flowing into the screen tube is subjected to cyclonic sand settling and cation aggregation to achieve the purpose of water control and sand removal; the fluid includes water and mud and sand; The cyclone sand settling method includes: gathering water and mud and sand flowing into the screen tube into a spiral tube; The cation aggregation method includes: arranging water control and sand removal devices at intervals along the length direction of the spiral tube, the water control and sand removal devices including two cation aggregation plates, the two cation aggregation plates being arranged opposite to each other, when the cation aggregation plates are energized, the anions are grounded and dissipated, and the cations are gathered on the cation aggregation plates to adsorb the mud and sand flowing through the spiral tube; At different mining periods, the purpose of slow or full discharge of mud and sand is achieved by controlling whether the cationic aggregation plates are energized.

2. The horizontal well water control and sand removal method according to claim 1, characterized in that: In the initial stage of mining, the cation aggregation plate is not energized, and the water and mud entering the screen pipe enter the wellbore through the production port of the screen pipe and are produced and collected on the ground.

3. The horizontal well water control and sand removal method according to claim 1 or 2, characterized in that: In the middle stage of mining, when water control and sand removal operations are required, the cationic aggregation plate is energized, and the mud and sand flowing through the spiral tube are adsorbed and gradually gathered, and the water flow channel in the spiral tube will gradually decrease, and the water volume will decrease accordingly.

4. The horizontal well water control and sand removal method according to claim 3, characterized in that: When the water volume decreases, the flow rate of the mud-containing liquid in the spiral tube decreases, and the mud and sand have sufficient time to undergo sedimentation reaction. The settled mud and sand will also reduce the flow space of the spiral sedimentator, increasing the pressure of the produced water flow and achieving the purpose of water control.

5. The horizontal well water control and sand removal method according to claim 1 or 2, characterized in that: In the later stage of mining, if the power supply of the cation aggregation plate is stopped or reduced, the cation aggregation plate loses or reduces its adsorption capacity for mud and sand, and the mud and sand accumulated on the cation aggregation plate begin to decompose and move with the water flow. The production channel of the spiral tube is gradually released, the water flow increases, the liquid flow rate in the spiral tube increases, and the mud and sand are also carried into the wellbore. The water-bearing profile drives the gas reservoir around the wellbore into the wellbore.

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