A method for reusing a gas storage reservoir cap layer cementing quality unqualified old well

Abstract

The application discloses a kind of old well reusing method of gas storage cover layer cementing quality unqualified, belong to gas storage old well reusing technical field, to explore how to carry out the reuse of gas storage cementing quality unqualified old well, the old well reusing method of gas storage cover layer cementing quality unqualified is aimed at the old well of gas storage cover layer section cementing quality unqualified, by forging milling treatment cover layer section original casing, then lower into small diameter gas seal casing or tubing for secondary cementing and reperforation, lower into gas production or monitoring completion pipe column, can realize the repair and reuse of unqualified old well, solve the high cost and resource waste problem caused by old well plugging and new well construction in the process of gas storage construction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas storage old well reutilization, in particular to a method for reutilization of gas storage cap layer cementing quality unqualified old well. BACKGROUND

[0002] The construction of gas storage in China is in a leapfrog development stage, and the problems of large-scale and rapid expansion of gas storage construction, safety awareness and ability, complex geological conditions, large injection and production, ultra-high load operation, reliability of equipment and construction quality, and multi-cycle long-term service have brought severe challenges to the risk control and safe operation of gas storage, and how to construct gas storage safely, with high quality and economically has become a key problem in the process of gas storage construction.

[0003] The selection of the site of the gas storage, especially the depleted oil and gas reservoir type gas storage, is usually an old exploration and development area, and all the completed wells drilled in the scope of the old area to reach the gas storage reservoir need to be effectively plugged or disposed for reutilization, which is also a prerequisite for the construction of the gas storage. The plugging of the old well of the depleted oil and gas reservoir type gas storage abroad generally follows the principle of "first difficult and then easy", that is, the old well in the depleted gas field is first evaluated, the most complex old well is first plugged, and then disposed in turn until all the old wells are successfully disposed before the construction of the gas storage is formally started, so as to avoid the situation that the construction of the entire gas storage is affected by the failure of the disposal of one well.

[0004] The research on the reutilization of the old well is a subject of improving the utilization efficiency and saving resources. In order to ensure the safe and efficient operation of the gas storage, new wells are generally drilled to ensure safety, and old wells are less used for networking. However, individual gas storages are located in farmland, grassland or nature reserves close to cities, and it is difficult to approve new wells for construction. Some gas storages have a large number of old wells, even hundreds of old wells, and the cementing quality of some old well cap layers cannot meet the reutilization standard, but if all the old wells are plugged and disposed, there will be problems of large workload, high cost and resource waste. SUMMARY

[0005] In order to explore the problem of how to carry out the reutilization of the old well with unqualified cementing quality of the gas storage, the present application provides a method for reutilization of the old well with unqualified cementing quality of the cap layer of the gas storage. The method for reutilization of the old well with unqualified cementing quality of the cap layer of the gas storage is used for the old well with unqualified cementing quality of the cap layer of the gas storage, the original casing in the cap layer is treated by forging and milling, a small-diameter gas-tight casing or tubing is lowered to carry out secondary cementing and re-perforation, and a gas production or monitoring completion pipe string is lowered, so that the unqualified old well can be repaired and reused, and the problems of high cost and resource waste caused by the plugging of the old well and the construction of new wells in the process of the construction of the gas storage are solved.

[0006] The technical solution adopted by the present application to solve the technical problems is:

[0007] A method for reusing an old well with unqualified cementing quality of a gas reservoir cap layer, comprising the following steps:

[0008] Step 1, selecting a target old well;

[0009] Step 2, scraping the original casing and plugging the original perforation position;

[0010] Step 3, forging and milling the original casing located in the cap layer to expand the original cementing area located in the cap layer in the target old well;

[0011] Step 4, lowering a new casing into the target old well, injecting cementing slurry between the new casing and the original casing, and implementing secondary cementing to form a secondary cementing area;

[0012] Step 5, connecting the new casing to the upper end of the target old well;

[0013] Step 6, perforating the new casing to form a new perforation position, the new perforation position being located in the reservoir to communicate the inside of the new casing with the reservoir, and lowering a completion string into the new casing;

[0014] Step 7, installing a new wellhead.

[0015] The method has the advantages that for the old well with unqualified cementing quality of the gas reservoir cap layer, the original casing in the cap layer is treated by forging and milling, a small-diameter gas-tight casing or tubing is lowered for secondary cementing and re-perforation, a gas production completion string or a monitoring device is lowered to monitor the cap layer, the plugging effect, and the downhole temperature and pressure in real time, the method can solve the problems of high cost and resource waste caused by plugging of the old well and construction of a new well during construction of the gas reservoir, is closely combined with the actual engineering, and has high practical value. BRIEF DESCRIPTION OF DRAWINGS

[0016] The drawings accompanying the specification of this application form a part hereof, serve to provide further understanding of the application, and together with the description of the application, explain the application.

[0017] Figure 1 is a front view of the target old well.

[0018] Figure 2 is a front view of forging and milling the original casing located in the cap layer.

[0019] Figure 3 is a front view of expanding the original cementing area located in the cap layer.

[0020] Figure 4 is a front view of lowering the new casing and implementing secondary cementing.

[0021] Figure 5is a top view schematic diagram of the original casing and the new casing.

[0022] Reference signs are explained as follows:

[0023] 1. original casing; 2. original cementing area; 3. borehole; 4. cap rock; 5. reservoir; 6. new casing; 7. secondary cementing area; 8. new wellhead; 9. hanger. DETAILED DESCRIPTION

[0024] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with embodiments.

[0025] A method for reusing a gas storage cap rock cementing quality unqualified old well, comprising the following steps:

[0026] Step 1, selecting a target old well;

[0027] In step 1, the selected target old well (i.e. the old well suitable for reuse) is a well whose original cementing area 2 is qualified in all parts except the part located in the cap rock 4, and which has the condition of being able to be reused after the old well is repaired, and the spatial structure of the target old well can meet the construction installation conditions, such as Figure 1 as shown in the figure.

[0028] The old well contains an original casing 1, an original cementing area 2 and a borehole 3, the lower end of the old well is located in the upper and lower cap rock 4 and the reservoir 5, the diameter of the original casing 1 can be 5 1 / 2" (139.7mm), and whether the quality of each part of the original cementing area 2 is qualified can be realized by RBT or ultrasonic cementing quality detection, that is, the RBT or ultrasonic cementing quality detector is lowered into the old well, and the method is used to detect whether the quality of the original cementing area 2 is qualified, which is the prior art.

[0029] Step 2, scraping the original casing 1, ensuring that the excess sludge in the wellbore is completely removed, and squeezing the original perforation part, which is usually located on the part of the original casing 1 corresponding to the reservoir 5;

[0030] Specifically, step 2 contains the following steps:

[0031] Step 2.1, pulling out the original well pipe column, if the original casing 1 contains the original well pipe column, the original well pipe column (including the original well production pipe column and the downhole mechanical bridge plug) is pulled out, if the original casing 1 does not contain the original well pipe column, the original well pipe column does not need to be pulled out;

[0032] Step 2.2, using a drift gauge to pass through the well, for example, using a drift gauge with a specification of 114mm to pass through the well, to exclude the risk of casing deformation;

[0033] Step 2.3, scraping the well, scraping the original casing 1 for 3 times at the original perforation site, in order to ensure that the excess sludge in the wellbore is completely removed, and the new casing 6 is smoothly lowered into the well, the caliper gauge is close to the perforation site and the pump is circulated normally, and then the active pipe column is repeatedly lifted and lowered for 3 times to scrape the casing;

[0034] Step 2.4, plugging the original perforation site on the original casing 1, using ultra-fine cement to plug the original perforation site according to the gas storage standard.

[0035] Step 3, forging and milling the original casing 1 located in the cap layer 4, the length of the forged and milled original casing 1 corresponds to the height of the cap layer 4, as shown in Figure 2 , the length of the forging and milling is not less than 50m, and the original cementing area 2 located in the cap layer 4 in the target old well is reamed, as shown in Figure 3 ;

[0036] Step 4, lowering the new casing 6 into the target old well, injecting cementing slurry into the annulus between the new casing 6 and the original casing 1, implementing secondary cementing, and forming a secondary cementing area 7, as shown in Figure 4 and Figure 5 ; selecting a suitable cementing slurry system to implement secondary cementing, after the cementing displacement is completed, the annulus is pressurized to plug the forged and milled section, and the setting is waited, the cementing quality is measured, and the quality of the secondary cementing area 7 is ensured;

[0037] In step 4, the new casing 6 is lowered into the target old well in a suspended manner, the diameter of the new casing 6 can be 3 1 / 2″(88.9mm), the new casing 6 can be a gas-tight casing or a tubing, the new casing 6 is connected with a hanger 9, and the new casing 6 is also connected with a centralizer. The upper end of the secondary cementing area 7 is higher than the cap layer 4, and the lower end of the secondary cementing area 7 is lower than the reservoir 5. The specific distance of the upper end of the secondary cementing area 7 from the cap layer 4 can be determined as needed, and the specific distance of the lower end of the secondary cementing area 7 from the reservoir 5 can be determined as needed.

[0038] Before lowering the new casing 6, the well needs to be carefully drilled and washed, and the drilling fluid performance needs to be fully adjusted. The casing material of the new casing 6 needs to be selected, the application of the centralizer needs to be combined when the new casing 6 is lowered, the centralization of the casing needs to be ensured, and the construction quality of the casing needs to be ensured. The application of the centralizer needs to be combined to maintain the centralization of the casing lowered into the wellbore.

[0039] In order to ensure the cementing quality of the secondary cementing area 7, the optimal cementing construction procedure needs to be designed, the wellbore needs to be optimized, the phenomenon of cement slurry channeling needs to be prevented, the best setting time needs to be determined in combination with the optimization of the cement slurry system, a stable cement sheath needs to be formed, and the quality requirements of cementing are met;

[0040] Step 5, back-connection of the new casing 6 to the upper end of the target old well, as shown inFigure 4 and Figure 5 as shown in

[0041] In step 5, the new casing 6 is run into the upper end of the target old well by using the back-connection sleeve, and step 5 also includes injecting the annulus protection fluid into the annulus between the original casing 1 and the new casing 6.

[0042] Step 6, perforating the new casing 6 to form a new perforation site, the new perforation site is located in the reservoir 5, so that the inside of the new casing 6 is in communication with the reservoir 5 through the new perforation site, and a new completion string is run into the new casing 6;

[0043] Step 7, installing a new wellhead 8, as shown in Figure 4 .

[0044] The method for reusing the old well with unqualified cementing quality of the gas storage cover layer is aimed at the old well with unqualified cementing quality of the gas storage cover layer section, through forging and milling the original casing of the cover layer section, then running the small-diameter gas-tight oil pipe to the artificial well bottom of the target old well, performing secondary cementing and re-perforating, running the gas production completion string or running the monitoring equipment to monitor the cover layer situation, plugging effect and downhole temperature and pressure in real time, fully utilizing the old well in the gas storage construction block, which can solve the problem of high cost and resource waste caused by plugging the old well and constructing the new well in the process of constructing the gas storage, and is closely combined with the actual engineering, and has high practical value.

[0045] The above is only a specific embodiment of the present application, which cannot limit the scope of the application, so the replacement of equivalent components or equivalent changes and modifications made within the scope of the patent protection of the present application should still belong to the scope covered by the present patent. In addition, the technical features in the present application can be freely combined with each other, and the technical features can be freely combined with each other, and the technical features can be freely combined with each other, and the technical features can be freely combined with each other.

Claims

1. A method for reusing a gas storage reservoir cap layer cementing quality unqualified old well, characterized in that, The method for reusing the old well with unqualified cementing quality of the cap layer of the gas reservoir comprises the following steps: Step 1, selecting a target old well; the selected target old well is an old well which can be reused after repair and has a spatial structure meeting the installation conditions, except that the quality of the original cementing area (2) in the cap layer (4) is unqualified; Step 2, scraping the original casing (1) in the well and plugging the original perforation position; Step 3, forging and milling the original casing (1) in the cap layer (4) and expanding the original cementing area (2) in the cap layer (4) in the target old well; Step 4, lowering a new casing (6) into the target old well in a suspended manner, the new casing (6) being connected with a centralizer, injecting cement slurry between the new casing (6) and the original casing (1), implementing secondary cementing, and forming a secondary cementing area (7); the upper end of the secondary cementing area (7) being higher than the cap layer (4), the lower end of the secondary cementing area (7) being lower than the reservoir (5), and the upper end of the secondary cementing area (7) being connected with the lower end of the hanger (9); Step 5, returning the new casing (6) to the upper end of the target old well; injecting annulus protection fluid into the annulus between the original casing (1) and the new casing (6); Step 6, perforating the new casing (6) to form a new perforation position, the new perforation position being located in the reservoir (5), the inside of the new casing (6) being communicated with the reservoir (5), and lowering a completion string into the new casing (6); Step 7, installing a new wellhead (8).

2. The method for reusing the gas reservoir cap rock cementing quality unqualified old well according to claim 1, characterized in that, Step 2 comprises the following steps: Step 2.1, pulling out the original well string.

3. The method of claim 2, wherein the method further comprises, Step 2 comprises the following steps: Step 2.2, using a drift gauge to pass through the well.

4. The method for reusing the gas reservoir cap rock cementing quality unqualified old well according to claim 3, characterized in that, Step 2 comprises the following steps: Step 2.3, scraping and washing the well, and scraping the original perforation position on the original casing (1) for three times.

5. The method for reusing the gas reservoir cap rock cementing quality unqualified old well according to claim 4, characterized in that, Step 2 comprises the following steps: Step 2.4, plugging the original perforation position on the original casing (1).

6. The method of claim 1, wherein the method further comprises, In step 3, the length of the forging and milling is not less than 50 m.

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