Method for fishing open hole sidetrack drilling of oil-string casing

Abstract

The invention relates to a method for fishing an open hole sidetrack of an oil-string casing, and belongs to the technical field of oil drilling and completion. The method comprises the following specific steps: establishing a fine geologic model according to different types of oil reservoir characteristics, and quantitatively researching remaining oil distribution; the oil-string casing is taken out from the downhole, the surface casing is reserved, and meanwhile, a navigation gyroscope which is not interfered by magnetism is introduced, so that the downhole random windowing state is avoided; windowing from a wellhead, and finishing one-time windowing and window repairing by using a special tool; according to the formation lithology and track control requirements, a drilling tool combination and an orientation tool are selected, a wireless while-drilling instrument or a wired while-drilling instrument is adopted, the full-angle change rate is scientifically controlled, the well track is accurately controlled, and a new oil-string casing is tripped below a surface casing in an original well. And a targeted sidetracking well completion method is formulated for different types of oil reservoirs. According to the method, existing resources are utilized, capital investment is reduced, drilling footage is mainly reduced, existing ground pipe networks and equipment are utilized, and tedious work such as land occupation is reduced.

Description

Technical Field

[0001] The present invention relates to a method for salvaging and sidetracking in the open hole of an oil layer casing, belonging to the technical field of oil drilling and completion. Background Art

[0002] The open hole sidetracking method is to inject a cement plug in the wellbore and sidetrack a new wellbore through this cement plug. In order to successfully sidetrack a new wellbore, the cement plug, as a support platform, must have sufficient strength; otherwise, it cannot provide the necessary support force for sidetracking. This is particularly important for hard formations because if the strength of the cement plug is insufficient, the drill bit will drill off the cement plug without sufficient support, resulting in the failure of sidetracking. Especially in deep wells, due to abnormal formation high temperature, wellbore shrinkage, and large bellies, the quality of the cement plug will be affected. Sidetracking is a process of deviating the drilling trajectory of the drill bit from the original wellbore trajectory according to a pre-designed path on the basis of the original wellbore trajectory (vertical well, directional well, or horizontal well) for special technological needs, using special sidetracking tools.

[0003] In view of the actual situation that in the late stage of oilfield development, the number of damaged casings and dropped objects in wells increases, the well conditions deteriorate, and the utilization rate of oil wells decreases, and for the characteristics of high requirements for new well drilling rigs, long well construction periods, high land acquisition and pre-drilling costs in aspects such as exploiting difficult-to-produce reserves and increasing reserves and production, the present invention proposes a technology for salvaging and open hole sidetracking of oil layer surface casings. Summary of the Invention

[0004] The present invention discloses a method for salvaging and open hole sidetracking of an oil layer casing, aiming at engineering abandoned wells and low-yield and low-efficiency wells, tapping the potential of remaining oil, increasing recoverable reserves, and improving the development level of the block.

[0005] The technical solution adopted by the present invention is a method for salvaging and open hole sidetracking of an oil layer casing, and the specific steps are as follows:

[0006] Step 1: Establish a fine geological model according to the characteristics of different types of oil reservoirs, and quantitatively study the distribution of remaining oil;

[0007] Step 2: Remove the oil layer casing from the well, retain the surface casing, and at the same time introduce a navigation gyroscope that is not magnetically interfered to avoid the random window-opening state in the well; open a window from the wellhead and use special tools to complete the first window-opening and window-repairing;

[0008] Step 3: Select a drill string assembly and a directional tool according to the formation lithology and trajectory control requirements, use a wireless measurement-while-drilling instrument or a wired measurement-while-drilling instrument, scientifically control the full angle change rate, accurately control the wellbore trajectory, and run a new oil layer casing below the surface casing in the original wellbore;

[0009] Step 4: Develop a targeted sidetracking completion method according to different types of oil reservoirs.

[0010] Further, the first step specifically includes establishing a fine geological model using Petrel software according to the characteristics of different types of reservoirs, describing the reservoir structural features, sedimentary facies, oil layers, porosity, and the planar and vertical distributions of permeability, dividing the reservoir into several grids, and quantitatively calculating the remaining reserves by the difference between the reserves and cumulative oil production of each grid to clarify the remaining oil distribution.

[0011] Further, in the first step, based on the Petrel geological model, a numerical model is established to predict the productivity of the sidetrack well through numerical simulation.

[0012] Further, in the second step, the special tools specifically include a whipstock and a milling cone.

[0013] Further, in the third step, the considerations for selecting the drill string assembly and directional tools include aspects of quality, technology, safety, and environmental protection.

[0014] Further, in the first step, the productivity prediction of the sidetrack well needs to meet the following conditions:

[0015] (1) Reservoir confirmed: The deployment target is located in a favorable part of the sedimentary facies belt, the thickness of the oil layer in the vertical well is greater than 20 meters, more than 50 meters away from the fault, and more than 100 meters away from the edge water;

[0016] (2) Reasonable well spacing: Deployed between wells, more than 50m away from the original well spacing, and maintaining a reasonable well spacing with the surrounding adjacent wells.

[0017] Further, in the first step, the productivity prediction of the sidetrack well also needs to meet the following conditions:

[0018] (3) Remaining oil known: The recovery degree of the deployment area is lower than the block index, and the remaining recoverable reserves in the area are greater than 3000 tons;

[0019] (4) Technically and economically feasible: There are old wells with casing damage, dropped objects, or no remaining layers available for sidetracking. The sidetracking parameter design can be achieved in engineering and the predicted economic benefit index is good.

[0020] Further, the fourth step includes methods such as liner cementing completion, upper cementing, lower screen pipe, and gravel packing completion.

[0021] The present invention discloses a method for salvaging and sidetracking in the open hole of an oil production casing. The beneficial effect is that the present invention utilizes existing resources such as shut-down and abandoned wells, low-yield and inefficient old wells, reduces capital investment, mainly reduces the drilling footage, and utilizes the existing surface pipe network and equipment to reduce cumbersome work such as land acquisition. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 The following is a schematic diagram of the original well;

[0024] Figure 2 The following is a schematic diagram of the downhole situation after salvaging the oil layer casing in Embodiment 1;

[0025] Figure 3 The following is a schematic diagram of the downhole situation after sidetracking in Embodiment 1.

[0026] As shown in the figure:

[0027] 1. Surface casing; 2. Original well oil layer casing; 3. Perforated interval of the production well; 4. Remaining position; 5. Sidetrack well oil layer casing. Detailed implementation manners

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, rather than all, embodiments of the present invention. The description of at least one exemplary embodiment is actually only illustrative and in no way restricts the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0029] To further understand the content of the present invention, the following will further elaborate on the present invention in combination with the specific implementation manners.

[0030] Embodiment 1:

[0031] Based on the existing development well pattern in the oil reservoir, find available old wells, such as Figure 1 As shown, it includes a surface casing 1, an original well oil layer casing 2, and a perforated interval of the production well. The surface casing 1 is sleeved outside the original well oil layer casing 2, and the downhole is the perforated interval of the production well; Figure 2 Take out the original well oil layer casing 2 from the downhole in Figure 3As shown, the side drilling well oil layer casing 5 is side-drilled to the target layer. Specifically, according to the characteristics of different types of oil reservoirs, the Petrel software is used to establish a fine geological model to describe the reservoir structure characteristics, sedimentary phase, oil layer, porosity, permeability plane and vertical distribution, and the oil reservoir is divided into several grids. Through the difference between the reserves and the cumulative oil production of each grid, the remaining reserves are quantitatively calculated to clarify the distribution of remaining oil. Based on the Petrel geological model, a numerical model is established to predict the productivity of the side drilling well through numerical simulation.

[0032] The oil layer casing is taken out from the well, and the surface casing 1 is retained. At the same time, a navigation gyroscope that is not affected by magnetic interference is introduced to avoid arbitrary window opening in the well; the window is opened from the wellhead, and special tools such as the guide bevel and milling cone are used to complete the window opening and repair; according to the formation lithology and trajectory control requirements, the four aspects of quality, technology, safety and environmental protection are comprehensively considered, and the drilling tool assembly and directional tools are selected. Wireless or wired drilling instruments are used to scientifically control the full-angle change rate, accurately control the wellbore trajectory, and insert a new oil layer casing below the surface casing 1 in the original wellbore. Targeted sidetracking completion methods are formulated for different types of oil reservoirs, mainly including liner cementing completion, upper cementing, lower screen and gravel packing completion methods.

[0033] Furthermore, in step 1, the prediction of the sidetrack well production capacity must meet the following conditions:

[0034] (1) Reservoir implementation: The deployment target is located in a favorable part of the sedimentary facies belt, with a vertical well oil layer thickness greater than 20 meters, more than 50 meters away from the fault, and more than 100 meters away from the edge water;

[0035] (2) Reasonable well spacing: Deployed between wells, more than 50m away from the original well, and maintain a reasonable well spacing with surrounding adjacent wells.

[0036] (3) Remaining oil shows that: the recovery degree of the deployment area is lower than the whole block index, the remaining recoverable reserves in the area are greater than 3,000 tons, and the oil wells in the deployed target layer have a high production before they are shut down;

[0037] (4) Technical and economic feasibility: Side drilling can be carried out in old wells with casing damage, fallen objects or no remaining layers. The side drilling parameter design can be achieved in engineering and the predicted economic benefit indicators are good.

[0038] By adopting the method of the present invention, the evaluation and exploration of new areas can be accelerated, and money can be saved and benefits can be created; the difficult-to-extract reserves can be used to play a great role; the well site deployment of the old area can be promoted to expand the well site, and new well sites can be brought out. In view of the problem that the side drilling technology in the traditional development concept is only used for the potential of residual oil between wells, the implementation goals of the stratum exchange are limited, and the effect is gradually getting worse, by adjusting the deployment ideas, a transformation to multiple goals, multiple uses, and multiple fields such as improving the well network, implementing production capacity, increasing reserves, and taking into account oil and gas is achieved.

[0039] From 2012 to 2014, 429 well-times were implemented in 3 blocks, with a cumulative incremental oil production of 562,000 tons in the stage. Table 1 is the classification table of different implementation objectives of sidetracking wells from 2012 to 2014. The change in the deployment idea and the diversification of deployment objectives of sidetracking wells have played an important role in alleviating the decline in old areas, making up for the shortage of new wells, and promoting exploration and reserve growth. Compared with the implementation of new wells, sidetracking wells save about 1 / 2 - 2 / 3 of the investment.

[0040] Table 1: Classification Table of Different Implementation Objectives of Sidetracking Wells from 2012 to 2014

[0041]

[0042] Using the old well L66C for sidetracking to understand the new area reserves. Table 2 is the comparison table of the investment details of the sidetracking well L66C and the new well L81. Compared with the exploration well L81 in terms of investment, 1.35 million yuan of investment is saved (950,000 yuan for drilling investment, 400,000 yuan for saving the well site fee for pad wells, and 300,000 yuan for saving casing and Christmas tree).

[0043] Table 2: Comparison Table of Investment Details of Sidetracking Well L66C and New Well L81

[0044]

[0045] For the areas with difficult-to-produce reserves, taking the sidetracking technology as the starting point of the development deployment work, the gravel packing completion technology was introduced for the first time. Table 3 is the application of the sidetracking technology in the difficult-to-produce reserves of Block W83, bringing out 14 new well positions, with 1.2 million tons of geological reserves being put into production, realizing the overall development of the difficult-to-produce block.

[0046] Table 3: Application of Sidetracking Technology in Difficult-to-Produce Reserves of Block W83

[0047]

[0048] The present invention mainly aims at old oilfields where due to long-term production, steam injection, stimulation, workover and other operations in oil wells, the casing damage increases and the well conditions deteriorate; at the same time, with the accelerating decline of oilfield production, the production capacity of production wells deteriorates year by year, the difficulty of oilfield reserve replacement increases, and the stable production situation of the oilfield is severe. Through years of on-site practical experience, the deployment of sidetracking wells must meet three conditions: controllable geological body, knowable remaining oil, and technically and economically feasible, and an optimized design concept for sidetracking wells has been formed, effectively guiding the deployment of sidetracking well plans.

[0049] The present invention utilizes existing resources such as shut-down and abandoned wells, low-yield and inefficient old wells, etc., to reduce capital investment, mainly by reducing the drilling footage, and utilizes the existing surface pipe networks and equipment to reduce cumbersome work such as land acquisition.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for salvaging and sidetracking in the open hole of an oil layer casing, characterized in that, the specific steps are as follows: Step 1, establish a fine geological model according to the characteristics of different types of oil reservoirs, and quantitatively study the remaining oil distribution; Step 2, remove the oil layer casing from the wellbore, retain the surface casing, and introduce a navigation gyroscope that is not magnetically interfered to avoid random windowing in the wellbore; open a window from the wellhead and use special tools to complete the first window opening and window repair; Step 3, select a drill string assembly and a directional tool according to the formation lithology and trajectory control requirements, use a wireless measurement-while-drilling instrument or a wired measurement-while-drilling instrument, scientifically control the rate of change of the full angle, accurately control the wellbore trajectory, and run a new oil layer casing below the surface casing in the original wellbore; Step 4, formulate a targeted sidetracking completion method for different types of oil reservoirs.

2. The method for salvaging and sidetracking in the open hole of an oil layer casing according to claim 1, characterized in that, Step 1 specifically includes establishing a fine geological model according to the characteristics of different types of oil reservoirs, using Petrel software to describe the reservoir structure characteristics, sedimentary facies, oil layers, porosity, permeability in the plane and longitudinal directions, dividing the oil reservoir into several grids, and quantitatively calculating the remaining reserves by the difference between the reserves of each grid and the cumulative oil production, and clarifying the remaining oil distribution.

3. The method for salvaging and sidetracking in the open hole of an oil layer casing according to claim 2, characterized in that, Step 1, on the basis of establishing a fine geological model in Petrel software, establish a numerical model, and predict the productivity of the sidetracked well through numerical simulation.

4. The method for salvaging and sidetracking in the open hole of an oil layer casing according to claim 1, characterized in that, In Step 2, the special tools specifically include a whipstock and a milling cone.

5. The method for salvaging and sidetracking in the open hole of an oil layer casing according to claim 1, characterized in that, In Step 3, the considerations for selecting a drill string assembly and a directional tool include aspects of quality, technology, safety and environmental protection.

6. The method for salvaging and sidetracking in the open hole of an oil layer casing according to claim 3, characterized in that, In Step 1, the productivity prediction of the sidetracked well needs to meet the following conditions: (1) Reservoir is well-defined: The deployment target is located in a favorable part of the sedimentary facies belt, the thickness of the vertical well oil layer is greater than 20 meters, more than 50 meters away from the fault, and more than 100 meters away from the edge water; (2) Well spacing is reasonable: Deployed between wells, more than 50m away from the original well well spacing, and maintain a reasonable well spacing with the surrounding adjacent wells.

7. The method for salvaging and sidetracking in the open hole of an oil layer casing according to claim 6, characterized in that, In Step 1, the productivity prediction of the sidetracked well also needs to meet the following conditions: (3) Remaining oil is known: The recovery degree of the deployment area is lower than the block index, and the remaining recoverable reserves in the area are greater than 3000 tons; (4) Technically and economically feasible: There are old wells with casing damage, falling objects or no remaining layers available for sidetracking, and the sidetracking parameter design can be achieved in engineering and the predicted economic benefit index is good.

8. The method for salvaging and sidetracking in the open hole of an oil layer casing according to claim 1, characterized in that, In Step 4, formulating a targeted sidetracking completion method for different types of oil reservoirs specifically includes the methods of liner cementing completion, upper cementing, lower screen pipe and gravel packing completion.

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