Drilling Method for Storage Well for Liquid-Gas Two-Phase Combined Geological Storage

This application is based upon and claims priority to Chinese Patent Application No. 202410757169.5, filed on Jun. 13, 2024, the entire contents of which are incorporated herein by reference.

The present disclosure belongs to the technical field of geological storage, and in particular to a drilling method for a storage well for liquid-gas two-phase combined geological storage.

Deep geological storage refers to storing gas or liquid into underground rock pores and micro-cracks at a depth of 1,500-3,500 meters below the earth surface through storage wells, such a depth ensures that the gas/liquid fluids are positioned outside the biosphere, and the sealing and degradation properties of the fourth-class environmental medium (deep geological environment) are utilized to prevent the sequestered fluids from participating in the material cycles of humans and living organisms. Deep geological storage is a safe environmental disposal method, which primarily involves the separate geological storage of gas or liquid in geological formations at present, followed by research on their subsurface migration and diffusion mechanisms. Moreover, the research on the foregoing aspects is relatively mature. However, there are few studies on gas-liquid mixed fluid or gas-liquid combined storage, for example, how to carry out gas-liquid combined storage of wastewater containing waste gas, and how to achieve combined storage of separate gas and liquid. At present, the main problems in this aspect are an unreasonable structure of a storage well, a sealing problem of the storage well, a problem of gas-liquid separation, and so on.

For the problem above, the present disclosure provides a drilling method for a storage well for liquid-gas two-phase combined geological storage, including following steps:

In some embodiments, each of the first bases comprises a first base sleeve and a first hanging ring. The first base sleeve is a hollow cylinder. An axial direction of the first base sleeve is perpendicular to an inner wall of a corresponding one of the multiple segments of second section sub-well casings. One end of the first base sleeve is provided with a circle of skirt edge extending vertically outwards. The circle of skirt edge is able to be attached to the inner wall of a corresponding one of the multiple segments of second section sub-well casings and is fastened to the inner wall of the corresponding one of the multiple segments of second section sub-well casings by bolts, thereby fastening the first base sleeve; and the first hanging ring is inside the first base sleeve and is installed on the inner wall of the corresponding one of the multiple segments of second section sub-well casings.

A formation depth of the gas storage layer is less than formation depth of the liquid storage layer, and a length of the second section well casing is less than a length of the third section well casing.

In step S3, a drill bit is drilled to the bottom of the gas storage layer, and a circular platform which is horizontal is formed at the bottom of the gas storage layer.

The second section sub-well casing at the bottom has a circular bottom surface and is correspondingly placed on the circular platform at the bottom of the gas storage layer.

A diameter of a drill bit adopted in step S3 is greater than that a diameter of a drill bit adopted in step S5. In steps S3 and S5, the second section well casing is concentrically arranged with the third section well casing and the first section well casing.

The drill bit adopted in step S5 starts to drill down from the drill-through hole of at the bottom surface of the second section sub-well casing at the bottom to the bottom of the liquid storage layer. A gap between an outer wall of the third section sub-well casing corresponding to the drill-through hole and an edge of the drill-through hole is sealed with the mud to prevent the gas in the second section well casing from leaking from the gap, and the third section well casing is also able to be reinforced and supported at the drill-through hole.

In some embodiments, a structure of the second base is the same as that of the first base. Specifically, each of the multiple second bases comprises a second base sleeve and a second hanging ring, the second base sleeve is a hollow cylinder. An axial direction of the second base sleeve is perpendicular to an inner wall of a corresponding one of the multiple segments of third section sub-well casings. One end of the second base sleeve is provided with a circle of skirt edge extending vertically outwards, the circle of skirt edge is able to be attached to an outer wall of the corresponding one of the multiple segments of third section sub-well casings and is fastened to the outer wall of the corresponding one of the multiple segments of third section sub-well casings by bolts, thereby fastening the second base sleeve; and the second hanging ring is inside the second base sleeve and is installed on the outer wall of the corresponding one of the multiple segments of third section sub-well casings.

In some embodiments, the gas-liquid separation component is a helical flow tube which surrounds an inner wall of the third section well casing in a helical pattern for multiple turns, and a top of each turn of the helical flow tube is provided with a hollowed-out vent slot for venting gas after gas-liquid separation, and the vent slot is arranged along the helical flow tube.

A liquid delivery pipe is arranged at a wellhead of the third section well casing, which extends from the ground to a top of the helical flow tube and is connected with a water inlet at the top of the helical flow tube. Liquid on the ground is input into the helical flow tube through the liquid delivery pipe and then flows downward along the helical flow tube, and a centrifugal force which is conducive to gas-liquid separation is generated. Separated gas is discharged from the vent slot, rises to an upper portion of the third section well casing, and then is discharged from the top of the third section well casing. A bottom end of the helical flow tube is open for the liquid to be drained into the third section well casing continuously. There are several support rods on the side, adjacent to the inner wall of the third section well casing, of the helical flow tube, which fix the helical flow tube on the inner wall of the third section well casing.

A method for arranging the support rod is as follows:

Each of the support rods is installed from bottom to top according to the method described above.

In some embodiments, in step (3), the multiple second bases and the multiple first bases are connected and positioned by the traction rope to avoid rotation dislocation of the third section sub-well casing in the hoisting process. In the process of descending the multiple segments of third section sub-well casings, the reel gradually retracts to make the traction rope gradually shortened, thereby preventing the traction rope from prolapsing and making the traction rope always kept in a tight state.

In some embodiments, in step (4), the free end of the traction rope is hung on a hoisting device, a top of each of the multiple sub-rods is temporarily connected with the hoisting device by at least two hoisting ropes, and the manipulator is pre-positioned by the retractable rod to a position beside the multiple first bases to be connected.

The hoisting device releases the sub-rod gradually. The sub-rod falls to a position beside the multiple first bases along the traction rope. The hoisting device moves towards a center of circle of the second section well casing on the ground, making a part of a root (that is a portion adjacent to the first base) of the traction rope horizontal, and the sub-rod is also in a horizontal posture with the traction rope.

A gripper of the manipulator grips the sub-rod to insert the sub-rod into the first base sleeve of a corresponding one of the multiple first bases, then the first base sleeve and the sub-rod are riveted or welded, and the hoisting rope connected with the sub rod is cut off by the manipulator.

In some embodiments, in step S6, the top of the third section well casing is closed with a well lid or cement, and a position for the liquid delivery pipe and a position for a vent pipe is reserved. The liquid delivery pipe is arranged adjacent to the inner wall of the third section well casing. One end of the vent pipe communicates with an inside of the third section well casing, and an other end of the vent pipe is connected with a gas delivery pipe to input separated gas in the third section well casing into the second section well casing.

In some embodiments, in step S6, the top of the second section well casing is closed with cement or a cover plate to achieve a sealing effect, thereby preventing the gas in the second section well casing from overflowing.

List of the reference characters:first section well casing;second section well casing;third section well casing;first base;second base;support rod;vent hole;drain hole;gas storage layer;liquid storage layer;drill-through hole;gas-liquid separation component;gas delivery pipe;liquid delivery pipe;circular platform;vent slot;traction rope;reel;sub-rod;manipulator; andretractable rod.

The present disclosure provides a drilling method for a storage well for liquid-gas two-phase combined geological storage, as shown into, including the following steps.

In S1, it is drilled down from a ground to the bottom of a potable aquifer, then a first section well casingis placed, and then cementing is carried out;

In S2, a second section well casingis divided into multiple segments of second section sub-well casings, multiple first basesare arranged on an inner wall of the second section sub-well casing in advance for installing support rodsbetween an inner wall of the second section well casingand an outer wall of a third section well casing.

A sidewall of the second section sub-well casing corresponding to a gas storage layeris uniformly provided with multiple vent holesfor venting a gas injected from the second section well casinginto the gas storage layer. A bottom surface of the second section sub-well casing at the bottom is closed and is provided with a drill-through holeat the center of the bottom surface for the third section well casingto pass through.

In S3, it is continued to drill down through the first section well casingto the bottom of the gas storage layer, then the second section well casing is placed in the first section well casing. The second section well casingextends to the bottom of the gas storage layerfrom the ground.

In S4, the third section well casingis divided into multiple segments of third section sub-well casings, and multiple second basesare arranged on an outer wall of the third section sub-well casing in advance for installing the support rods.

A gas-liquid separation componentis arranged in any one of third section sub-well casings at an upper portion of the third section well casingfor gas-liquid separation of liquid injected from the third section well casing. A sidewall of the third section sub-well casing corresponding to the liquid storage layeris uniformly provided with multiple drain holesfor draining the liquid injected from the third section well casinginto the liquid storage layer.

In S5, it is continued to drill down through the second section well casingto the bottom of the liquid storage layer, then the third section well casingis placed in the second section well casing. The third section well casingextends to the bottom of the liquid storage layerfrom the ground, and outside a position where the third section well casingpenetrates the drill-through hole, the outer wall of the third section well casingand an edge of the drill-through holeare sealed with mud.

The second baseson the outer wall of the third section sub-well casing are in one-to-one correspondence with the first bases, and then the support rods are installed.

In S6, the top of the second section well casingis closed, and a position for the top of the third section well casing and at least one wellhead of the second section well casing is reserved. The top of the third section well casing is closed, and a position for a wellhead of the third section well casing reserved.

A drilling technology in steps S1, S3 and S5 is the prior art. In step S1, a length of the first section well casingis relatively short, which may be a whole section of well casing, or may be formed by vertically connecting multiple segments of first section sub-well casings. Cementing is the prior art, that is, an outer wall of the first section well casingis protected and sealed with the mud to fasten a position of the first section well casing.

In some embodiments, the first baseincludes a first base sleeve and a first hanging ring. The first base sleeve is a hollow cylinder. An axial direction of the first base sleeve is perpendicular to the inner wall of the second section sub-well casing. One end of the first base sleeve is provided with a circle of skirt edge extending vertically outwards. The skirt dage can be attached to the inner wall of the second section sub-well casing and is fastened to the inner wall of the second section sub-well casing by bolt. thereby fastening the first base sleeve. The first hanging ring is in the first base sleeve and installed on the inner wall of the second section sub-well casing.

In step S2, a length of the second section well casingis relatively long, which is divided into multiple segments of second section sub-well casings connected up and down. A formation depth of the gas storage layeris less than that of the liquid storage layer, and a length of the second section well casingis less than that of the third section well casing.

In step S3, a drill bit is drilled to the bottom of the gas storage layer, and a horizontal circular platformis formed at the bottom of the gas storage layer. The second section sub-well casings are hoisted and placed into a drilled well section one by one from bottom to top, and the connecting between two second section sub-well casings is the prior art, and the second section well casingalso requires a conventional cementing operation.

Remaining second section sub-well casings are all opened at upper and lower ends, and only the second section sub-well casing at the bottom has a circular bottom surface, which is correspondingly placed on the circular platformat the bottom of the gas storage layer. The circular platformplays a role in supporting the second section well casings. The bottom surface of the second section sub-well casing at the bottom is closed except the drill-through hole, which can prevent the gas injected into the second section well casingfrom leaking downwards, such that the gas in the second section well casingcan be only discharged into the gas storage layerthrough the vent holes.

A diameter of a drill bit adopted in step S3 is greater than that of a drill bit adopted in step S5, that is, a diameter of the second section well casingis greater than that of the third section well casing. In steps S3 and S5, the second section well casingis concentrically arranged with the third section well casingand the first section well casing. The drill bit adopted in step S5 starts to drill down from the drill-through holeof at the bottom surface of the second section sub-well casing at the bottom to the bottom of the liquid storage layer, and the diameter of the drill bit adopted in step S5 is not greater than that of the drill-through hole. The third section sub-well casings are hoisted and placed into the drilled well section from bottom to top one by one, and then are installed on the ground in the second section well casing. The connection between the third section sub-well casings is the prior art, and the third section well casingalso requires a conventional cementing operation. In addition, a gap between an outer wall of the third section sub-well casing corresponding to the drill-through holeand the edge of the drill-through holeis sealed with the mud to prevent a gas in the second section well casingfrom leaking from the gap, and the third section well casingcan be reinforced and supported at the drill-through hole. For the sealing between the third section well casing and the drill-through hole, a circle of sealing ring may also be arranged on the outer wall of the third section well casing corresponding to the drill-through hole in advance. After the third section sub-well casing is placed in place, the sealing ring just corresponds to the drill-through hole, and the sealing purpose can also be achieved.

In some embodiments, the structure of the second baseis the same as that of the first base. Specifically, the second baseincludes a second base sleeve and a second hanging ring. The second base sleeve is a hollow cylinder. An axial direction of the second base sleeve is perpendicular to an inner wall of the third section sub-well casing. One end of the second base sleeve is provided with a circle of skirt edge extending outwards in a vertical direction. The skirt edge can be attached to the outer wall of the third section sub-well casing and is fastened to the outer wall of the third section sub-well casing by a bolt, thereby fastening the second base sleeve. The second hanging ring is in the second base sleeve and is installed on the outer wall of the third section sub-well casing.

In some embodiments, the gas-liquid separation componentis a helical flow tube which surrounds the inner wall of the third section well casingin a helical pattern for multiple circles, and the top of each turn of the helical flow tube is provided with a hollowed-out vent slotfor venting gas after gas-liquid separation, and the vent slotis arranged along the helical flow tube.

A liquid delivery pipeis arranged at the wellhead of the third section well casing, which extends from the ground to the top of the helical flow tube and is connected with a water inlet at the top of the helical flow tube. Liquid on the ground is input into the helical flow tube through the liquid delivery pipe, and then flows downward along the helical flow tube, and a centrifugal force which is conducive to gas-liquid separation is generated. A separated gas is discharged from the vent slot, rises to the upper portion of the third section well casing, and then discharged from the top of the third section well casing. A bottom end of the helical flow tube is open for continuously draining the liquid into the third section well casing. A side surface, adjacent to the inner wall of the third section well casing, of the helical flow tube is provided with multiple struts to fasten the helical flow tube to the inner wall of the third section well casing.

For the problem of the gas-liquid two-phase combined geological storage, the second section well casingand the third section well casingnested inside and outside are designed. The second section well casingextends to the bottom of the gas storage layer, the third section well casingis arranged inside the second section well casingand extends to the bottom of the liquid storage layer. The liquid is injected into the third section well casing through the wellhead of the third section well casingor the liquid delivery pipe, the gas is injected into a region between the second section well casingand the third section well casingthrough the wellhead of the second section well casingor the gas delivery pipe. The gas and the liquid are separated for respective injection without affecting with each other. The gas delivery pipeis arranged in the wellhead of the second section well casing, and extends into the second section well casingfrom the ground to connect gas delivery equipment.

According to the present disclosure, it is equivalent to saving the drilling cost of a portion, located in the second section well casing, of the third section well casing. However, as a portion of the third section well casingis in the second section well casing, if it is only fixed at the ground and the drill-through hole, the stability of the third section well casingwill be reduced. In particular, the gas-liquid separation componentis arranged in the third section well casing, and the helical flow of the liquid will produce centrifugal force, so there is a higher requirement on the stability of the third section well casing. Multiple support rodsare arranged between the walls of the second section well casingand the third section well casingfor supporting the third section well casing, and a method for arranging the support rodis as follows.

A corresponding traction ropeis connected to the first baseon the inner wall of the second section well casingaccording to a method in step (2).

The third section sub-well casing is hoisted into the second section well casingto connect the third section sub-well casing that has been installed and positioned below, and under traction and guidance of the traction rope, a correct orientation can be maintained when lowering the third section sub-well casing, making the second basescorrespond to the first basesone by one.

After installing all third section sub-well casings according to a method in step (3), all the hooks corresponding to the second basesare removed by the manipulatorand the retractable rodaccording to a method in step (2). One end, corresponding to the second base, of the traction ropeis recovered to the ground to form a free end, and then the third section well casingis cemented;

The support rodsare installed from bottom to top according to the method described above.

In some embodiments, in step (1), the traction ropeis wound in the reelin advance. The reelis the prior art, that is, both sides of the reelare respectively provided with an outlet, such that both ends of the traction ropecan extend out of the reel. The reelis internally provided with a rotating shaft, which is connected with a motor. The redundant traction ropeis wound on the rotating shaft, and the motor drives the rotating shaft to rotate forward or backward, thus achieving the winding or unwinding of the traction rope.

In some embodiments, in step (2), operating the retractable rodto ascend and descend is a conventional technology in the prior art. The manipulatorhas the function of moving and rotating in three dimensions, and can move within a short distance and a small range. Each of the hook and hanging ring can be provided with a locking structure to avoid unhooking.

In some embodiments, in step (3), the second baseand the first baseare connected and positioned in advance by the traction ropeto avoid rotation dislocation of the third section sub-well casing in the hoisting process. In the process of descending the third section sub-well casing, the reelgradually winds to make the traction ropegradually shortened, thus preventing the traction ropefrom prolapsing, and making the traction ropealways kept in a tight state.