Method for building salt cavern gas storage
阅读说明：本技术 盐穴储气库的建造方法 (Method for building salt cavern gas storage ) 是由 李建君 巴金红 王立东 王元刚 薛雨 周冬林 刘继芹 陈加松 齐得山 刘春� 何 于 2018-07-23 设计创作，主要内容包括：本发明公开了一种盐穴储气库的建造方法,属于石油天然气技术领域。该方法包括：在相互连通的两个盐穴的井筒的套管中分别设置桥塞；在桥塞上形成水泥塞；在水泥塞上方预定距离的套管管壁上进行锻铣以截断套管,露出岩层；在截断套管的位置进行扩眼,以在岩层中形成环形槽；在套管中形成水泥封堵；沿套管的轴向在水泥封堵上钻孔并插入新套管；采用水泥密封新套管和水泥封堵之间的间隙；从新套管内钻穿水泥塞和桥塞；在连通通道上方钻设与两个盐穴之间的连通通道连通的新井,从而将连通的盐穴改造为盐穴储气库。在存储天然气时,通过井筒中的新套管向盐穴中注入天然气,使盐穴中的卤水从新井中溢出,从而将天然气储存在形成的盐穴储气库中。(The invention discloses a method for building a salt cavern gas storage, and belongs to the technical field of petroleum and natural gas. The method comprises the following steps: respectively arranging bridge plugs in casings of the shafts of the two salt pits which are communicated with each other; forming a cement plug on the bridge plug; performing forging milling on the wall of the casing pipe above the cement plug by a preset distance to cut off the casing pipe and expose a rock stratum; reaming the casing at the location of the severed casing to form an annular slot in the formation; forming cement plugging in the casing; drilling a hole on the cement plug along the axial direction of the casing and inserting a new casing; sealing the gap between the new sleeve and the cement plug by using cement; drilling through cement plugs and bridge plugs from the new casing; and drilling a new well communicated with the communication channel between the two salt holes above the communication channel, so as to transform the communicated salt holes into the salt hole gas storage. When the natural gas is stored, the natural gas is injected into the salt cavern through a new casing in the shaft, so that brine in the salt cavern overflows from the new well, and the natural gas is stored in the formed salt cavern gas storage.)
1. A method of constructing a salt cavern gas storage, the method comprising:
respectively arranging bridge plugs in casings of the shafts of the two salt pits which are communicated with each other;
forming a cement plug on the bridge plug;
performing forging milling on the wall of the casing pipe above the cement plug by a preset distance to cut off the casing pipe and expose a rock stratum;
reaming at a location that intercepts the casing to form an annular groove in the formation extending radially outward of the casing;
forming a cement plug in the sleeve, wherein the top end of the cement plug is higher than the annular groove;
drilling a hole on the cement plug along the axial direction of the casing and inserting a new casing;
sealing a gap between the new casing and the cement plug by using cement;
drilling through the cement plug and the bridge plug from within the new casing;
and drilling a new well communicated with the communication channel between the two salt holes above the communication channel.
2. The method of constructing a salt cavern gas storage as claimed in claim 1, wherein drilling a new well above the communication channel in communication with the communication channel between the two salt caverns comprises:
determining the position of the communication channel according to the well track data of the two salt caverns;
and determining a target point on the communicating channel, and drilling towards the target point to form the new well.
3. The method of constructing a salt cavern gas storage as claimed in claim 2, further comprising:
after the new well is formed, water cavity construction operation is carried out at the bottom of the new well to form a water cavity communicated with the new well and the communication channel.
4. The method of constructing a salt cavern gas storage as claimed in claim 3, wherein the water-soluble cavity construction is performed at the bottom of the new well and comprises:
forming an initial water soluble cavity at the bottom of the new well through water soluble cavity forming operation;
performing water injection operation on the two salt caverns by taking a new casing in the shaft of the two salt caverns as an inlet, and stopping water injection when brine is discharged from the mouth of the new well;
when no brine is discharged from the new well mouth, the water-soluble cavity construction operation and the water injection operation are repeated until brine is discharged from the new well mouth.
5. The method of constructing a salt cavern gas storage as claimed in any one of claims 1 to 4, further comprising:
and after forming the cement plug on the bridge plug, carrying out pressure test on the cement plug.
6. The method of constructing a salt cavern gas storage as claimed in any one of claims 1 to 4, further comprising:
after sealing the gap between the new casing and the cement plug with cement, the new casing is pressure tested.
7. The method of constructing a salt cavern gas storage as claimed in any one of claims 1 to 4, further comprising:
before bridge plugs are respectively arranged in casings of shaft bodies of two mutually communicated salt caverns, the casings of the shaft bodies of the two salt caverns are pretreated to remove impurities in the casings of the shaft bodies of the two salt caverns.
8. The method for constructing a salt cavern gas storage as claimed in any one of claims 1 to 4, wherein the bridge plug is arranged 4 to 6m above the bottom end of the casing.
9. The method for constructing a salt cavern gas storage as claimed in any one of claims 1 to 4, wherein the length of the annular groove is 25 to 35m along the axial direction of the casing of the shaft of the two salt caverns.
10. The method for constructing a salt cavern gas storage as claimed in any one of claims 1 to 4, wherein before the step of respectively arranging bridge plugs in casings of well bores of two salt caverns which are communicated with each other, the method further comprises the following steps:
inverting the shape change process of the salt cavern and the shape of the space occupied by the insoluble residues according to the volumes of the two salt caverns, the volume occupied by the insoluble residues and the underground operation record during salt mine exploitation;
establishing a stability evaluation model of the salt cavern according to the inversion result, and determining the structural strength of each part in the salt cavern according to a stability criterion and a safety criterion;
the highest pressure that can be maintained when storing natural gas is determined from the structural strength.
Technical Field
The invention relates to the technical field of petroleum and natural gas, in particular to a method for building a salt cavern gas storage.
Background
The salt cavern is a cavern left after salt mining, is large in size and good in sealing, and can form a salt cavern gas storage for storing natural gas by modifying the salt cavern.
In the process of mining salt mines, a shaft is arranged, salt caverns are connected to the surface through the shaft, and usually only one shaft is arranged corresponding to one salt cavern. After the salt mine exploitation is finished, a new casing pipe is inserted into an old casing pipe of a shaft, so that the bottom of the new casing pipe is positioned under brine in a salt cavern, and the salt cavern can be transformed into a salt cavern gas storage. When natural gas is stored, natural gas can be injected into the salt cavern through the annular space between the old casing pipe and the new casing pipe, so that brine formed in the salt cavern is discharged from the new casing pipe until no brine is discharged, and a wellhead can be closed.
When salt mines are mined, the bottoms of two salt caverns are communicated sometimes, and mining is carried out by injecting water into one wellhead and extracting brine from the other wellhead, but the existing construction method of the salt cavern gas storage only aims at independent salt caverns, so that more communicated salt caverns are idle and cannot be utilized.
Disclosure of Invention
The embodiment of the invention provides a method for building a salt cavern gas storage, which is suitable for transforming communicated salt caverns into the salt cavern gas storage. The technical scheme is as follows:
the embodiment of the invention provides a method for building a salt cavern gas storage, which comprises the following steps:
respectively arranging bridge plugs in casings of the shafts of the two salt pits which are communicated with each other;
forming a cement plug on the bridge plug;
performing forging milling on the wall of the casing pipe above the cement plug by a preset distance to cut off the casing pipe and expose a rock stratum;
reaming at a location that intercepts the casing to form an annular groove in the formation extending radially outward of the casing;
forming a cement plug in the sleeve, wherein the top end of the cement plug is higher than the annular groove;
drilling a hole on the cement plug along the axial direction of the casing and inserting a new casing;
sealing a gap between the new casing and the cement plug by using cement;
drilling through the cement plug and the bridge plug from within the new casing;
and drilling a new well communicated with the communication channel between the two salt holes above the communication channel.
Optionally, drilling a new well above the communication channel in communication with the communication channel between the two salt caverns, comprising:
determining the position of the communication channel according to the well track data of the two salt caverns;
and determining a target point on the communicating channel, and drilling towards the target point to form the new well.
Optionally, the method further comprises:
after the new well is formed, water cavity construction operation is carried out at the bottom of the new well to form a water cavity communicated with the new well and the communication channel.
Optionally, said performing a water-soluble cavity-creating operation downhole of said new well comprises:
forming an initial water soluble cavity at the bottom of the new well through water soluble cavity forming operation;
performing water injection operation on the two salt caverns by taking a new casing in the shaft of the two salt caverns as an inlet, and stopping water injection when brine is discharged from the mouth of the new well;
when no brine is discharged from the new well mouth, the water-soluble cavity construction operation and the water injection operation are repeated until brine is discharged from the new well mouth.
Optionally, the method further comprises:
and after forming the cement plug on the bridge plug, carrying out pressure test on the cement plug.
Optionally, the method further comprises:
after sealing the gap between the new casing and the cement plug with cement, the new casing is pressure tested.
Optionally, the method further comprises:
before bridge plugs are respectively arranged in casings of shaft bodies of two mutually communicated salt caverns, the casings of the shaft bodies of the two salt caverns are pretreated to remove attachments on the casings of the shaft bodies of the two salt caverns.
Optionally, the bridge plug is arranged 4-6 m above the bottom end of the casing.
Optionally, the length of the annular groove is 25-35 m along the axial direction of the casing of the shaft of the two salt caverns.
Optionally, before the bridge plug is respectively arranged in the casings of the wellbores of the two salt caverns which are communicated with each other, the method further comprises the following steps:
inverting the shape change process of the salt cavern and the shape of the space occupied by the insoluble residues according to the volumes of the two salt caverns, the volume occupied by the insoluble residues and the underground operation record during salt mine exploitation;
establishing a stability evaluation model of the salt cavern according to the inversion result, and determining the structural strength of each part in the salt cavern according to a stability criterion and a safety criterion;
the highest pressure that can be maintained when storing natural gas is determined from the structural strength.
The technical scheme provided by the embodiment of the invention has the beneficial effects that at least: the bridge plugs are respectively arranged in the two sleeves, so that the cement plugs can be formed on the bridge plugs through the support of the bridge plugs, the pipe walls are forged and milled above the cement plugs, the pipe walls of the sleeves are cut to expose rock stratums, annular grooves are formed at the cut positions of the sleeves through reaming, when the cement plugs are formed in the sleeves, sealing can be formed between the cement plugs and the underground rock stratums, new sleeves are inserted after holes are drilled on the cement plugs, gaps between the new sleeves and the cement plugs are sealed by adopting cement, the new sleeves are fixed and sealed, the cement plugs and the bridge plugs are drilled through, the new sleeves are communicated with a salt cavern and a wellhead, a new well is drilled between shafts of the two salt caverns, the new well is communicated with a communication channel between the two salt caverns, and the communicated salt caverns are transformed into a salt cavern gas storage. When the natural gas is stored, the natural gas is injected into the salt caverns through the new casing pipes in the shaft of the two salt caverns, so that brine in the salt caverns overflows from the new well, and the natural gas is stored in the formed salt cavern gas storage.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart of a method for constructing a salt cavern gas storage according to an embodiment of the invention;
FIG. 2 is a flow chart of another method for constructing a salt cavern gas storage according to an embodiment of the invention;
FIGS. 3 to 5 are schematic diagrams illustrating a process of constructing a salt cavern gas storage according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a constructed salt cavern gas storage according to an embodiment of the invention;
fig. 7 is a top view of fig. 6.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Fig. 1 is a flow chart of a method for building a salt cavern gas storage according to an embodiment of the invention. As shown in fig. 1, the method includes:
s11: and respectively arranging bridge plugs in the casings of the shafts of the two salt pits which are communicated with each other.
S12: a cement plug is formed over the bridge plug.
S13: and performing forge milling on the wall of the casing pipe which is a preset distance above the cement plug to cut off the casing pipe and expose the rock stratum.
S14: reaming is performed at the location of the shut-off casing to form an annular groove in the formation extending radially outwardly of the casing.
S15: and forming a cement plug in the sleeve, wherein the top end of the cement plug is higher than the annular groove.
S16: and drilling a hole on the cement plug along the axial direction of the casing and inserting a new casing.
S17: and sealing the gap between the new casing and the cement plug by adopting cement.
S18: drilling through the cement plug and the bridge plug from the new casing.
S19: and drilling a new well communicated with the communication channel between the two salt holes above the communication channel.
The bridge plugs are respectively arranged in the two sleeves, so that the cement plugs can be formed on the bridge plugs through the support of the bridge plugs, the pipe walls are forged and milled above the cement plugs, the pipe walls of the sleeves are cut to expose rock stratums, annular grooves are formed at the cut positions of the sleeves through reaming, when the cement plugs are formed in the sleeves, sealing can be formed between the cement plugs and the underground rock stratums, new sleeves are inserted after holes are drilled on the cement plugs, gaps between the new sleeves and the cement plugs are sealed by adopting cement, the new sleeves are fixed and sealed, the cement plugs and the bridge plugs are drilled through, the new sleeves are communicated with a salt cavern and a wellhead, a new well is drilled between shafts of the two salt caverns, the new well is communicated with a communication channel between the two salt caverns, and the communicated salt caverns are transformed into a salt cavern gas storage. When the natural gas is stored, the natural gas is injected into the salt caverns through the new casing pipes in the shaft of the two salt caverns, so that brine in the salt caverns overflows from the new well, and the natural gas is stored in the formed salt cavern gas storage.
Fig. 2 is a flow chart of another method for constructing a salt cavern gas storage according to the embodiment of the invention. The construction of the salt cavern gas storage is described below with reference to fig. 3 to 7. As shown in fig. 2, the method includes:
s21: the casing of the wellbore of both salt caverns is pretreated.
After the salt mine is mined, more impurities such as silt and rust can be attached to the casing in the reserved shaft, the attachments can reduce the adhesive force between a bridge plug and the like arranged in the casing and the wall of the casing, and the casing can be blocked by the impurities falling into the well, so that the lowering of the bridge plug and the like is influenced. Therefore, a pre-treatment is required to remove debris from the casing of the wellbore in both salt caverns.
Alternatively, the pre-treatment may comprise drifting, scraping, by which the casing is ensured to be unobstructed, by which the casing wall is scraped, silt, rust etc. on the casing wall can be removed.
S22: and respectively arranging bridge plugs in the casings of the shafts of the two salt pits which are communicated with each other.
The following description will be given taking as an example the placement of a bridge plug in a casing. As shown in fig. 3, a
S23: a cement plug is formed over the bridge plug.
When the method is implemented, cement can be poured into the casing to form a cement plug with the length of 12-18 m. Illustratively, the length H of the cement plug may be 15 m. As shown in fig. 3, a
S24: the cement plug was pressure tested.
Alternatively, water injection manometry or gas injection manometry may be employed.
And in the water injection test, water is injected into the casing to form a water column with a preset height, the falling height of the water column in preset time is observed, if the falling height of the water column is within a preset range, the setting of the cement plug is qualified, if the falling height of the water column exceeds the preset range, the setting of the cement plug is unqualified, and the bridge plug and the cement plug are required to be reset after the cement plug and the bridge plug are removed.
And gas injection and pressure measurement, namely injecting gas with preset pressure into the casing, closing the casing, observing the value of the pressure reduction of the gas in preset time, if the value of the pressure reduction is within a preset range, indicating that the setting of the cement plug is qualified, and if the value of the pressure reduction is beyond the preset range, indicating that the setting of the cement plug is unqualified, and resetting the bridge plug and the cement plug after removing the cement plug and the bridge plug.
S25: the pipe wall above the cement plug is swaged a predetermined distance to cut the casing and expose the formation.
S26: reaming is performed at the location of the shut-off casing to form an annular groove in the formation extending radially outwardly of the casing.
After the forge mill exposes the subterranean formation, a ring-shaped recess is formed in the formation by reaming. The predetermined distance may be 15 to 20 m.
Optionally, the length d of the annular groove along the axial direction of the casing of the shaft of the two salt caverns can be 25-35 m. Illustratively, the annular groove may have a length of 30 m. As shown in fig. 4, an
S27: pouring superfine cement into the sleeve, and then building pressure and waiting to set to form cement plugging.
In practice, the top end of the cement block should be higher than the annular groove, so that the formed cement block has a section of outer flange (i.e. the part of the cement block located in the annular groove). As shown in FIG. 4, the top end of the
In the embodiment, the particle size of the superfine cement can be 0.2-20 μm, the superfine cement has a good waterproof and leaking stoppage effect, and the sealing performance can be improved by adopting the superfine cement to manufacture cement plugging.
Before pouring the superfine cement, the interior of the sleeve can be cleaned to remove impurities such as silt, broken stone and the like falling on the cement plug.
The cement plug can be subjected to pressure test after the cement plug is formed, during testing, water injection pressure measurement or gas injection pressure measurement can be adopted, and the testing method can be the same as the testing direction of the cement plug during pressure test. And if the test is unqualified, the cement plug is required to be removed and then pouring is carried out again.
S28: and drilling a hole on the cement plug along the axial direction of the casing and inserting a new casing.
When the method is implemented, the drill bit can be used for drilling 1.5-2 m above the bridge plug along the axial direction of the casing (as shown in a dotted line m in FIG. 4). After drilling, one end of a new casing 25 (see fig. 5) is inserted into the drilled hole and the other end of the
S29: and sealing the gap between the new casing and the cement plug by adopting cement.
The cement plug forms a section of cement sheath after drilling, so that the inner diameter of the cement sheath (namely the diameter of a hole drilled on the cement plug) is larger than the diameter of a new casing in order to facilitate the insertion of the new casing, a gap exists between the new casing and the cement sheath, and after the new casing is inserted into the hole, the gap can be sealed by adopting cement.
S30: the new casing was pressure tested.
During implementation, the pressure test can be performed on the new casing by adopting the water injection test or gas injection test method, and the new casing can be checked before being lowered, so that the structure of the new casing is intact without defects such as damage and cracks, and therefore if the pressure test is unqualified, the gap sealing between the new casing and the cement plug is not tight, and the cement pouring sealing needs to be performed again.
S31: drilling through the cement plug and the bridge plug from the new casing.
The new casing is made to communicate the salt cavern with the outside by drilling through the bridge plug, as shown in fig. 5.
S32: and determining the target point according to the well track data of the two salt caverns.
The communication channel between two salt caverns is usually formed by adopting a horizontal drill in the salt mine exploitation process, well trajectory data is usually reserved, and the position of the communication channel can be determined according to the well trajectory data.
S33: and determining a target point on the communicating channel, and drilling towards the target point to form a new well.
One point on the communicating channel can be selected as a target point, and after the target point is set, the new well can be communicated with the communicating channel at the target point by drilling towards the target point. As shown in fig. 6, the
Due to the scouring effect of brine in the communicating channel, the diameter of the communicating channel is increased to a certain extent when being formed compared with that when a horizontal drill is adopted in the salt mine exploitation process, but the diameter of the communicating channel is far smaller than that of a main body part of a salt cavern, the shape of the communicating channel cannot be accurately measured by a general geophysical logging method, the shape change of the salt cavity can be reversed according to the volume of the salt cavern, the content of insoluble substances and underground operation records, the shape of the communicating channel is predicted, and the target point can be conveniently determined by combining the shape of the communicating channel.
If the new well is drilled to a preset depth, water injection operation is carried out on the two salt caverns by taking the new casing in the shaft of the two salt caverns as an inlet, and when no brine is discharged from the new well, the construction method of the salt cavern gas storage can further comprise the following steps:
s34: after the new well is formed, water cavity making operation is carried out at the bottom of the new well to form a water cavity communicated with the new well and the communication channel.
As shown in fig. 6, the
When the cavity is formed by water, the following method can be specifically adopted:
and forming an initial water soluble cavity at the bottom of the new well through water soluble cavity forming operation. And (4) performing water injection operation in the two salt caverns by taking the new casing in the shaft of the two salt caverns as an inlet, and stopping water injection when brine is discharged from the well mouth of the new well. When no brine is discharged from the new well mouth, the water cavity construction operation and the water injection operation are repeated until brine is discharged from the new well mouth. For example, as shown in fig. 7, the
Through carrying out water-soluble chamber operation of making many times, enlarge the diameter in the initial water-soluble chamber that forms gradually, after carrying out water-soluble chamber operation of making at every turn, water injection in to the salt cavern through installing the new sleeve pipe in two wellholes, water can form brine after entering into the salt cavern, if there is brine to spill over from the new well head, then show the new well and communicate the passageway intercommunication, if do not have brine to spill over from the new well head, then the new well in surface and communicate the passageway and not have the intercommunication yet, still need continue to enlarge the diameter that the water-soluble chamber, dissolve chamber and communicate the passageway intercommunication until water.
After the new well is communicated with the communication channel, the salt cavern gas storage is built, as shown in fig. 6, natural gas can be injected into the
Alternatively, prior to step S21, sonar may be used to measure the volume of both salt caverns 41 (excluding the volume of
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.