Deep well drilling method

Abstract

The present invention provides a deep well drilling method, which includes: drilling the upper formation to a preset formation depth and performing cementing; performing under-reaming while drilling on the lower formation and performing cementing; drilling and cementing the remaining formation; the performing under-reaming while drilling on the lower formation includes: using a drill string assembly for under-reaming while drilling to perform N trips; the drill string assembly for under-reaming while drilling includes a PDC bit, a screw drill, and an under-reamer arranged from bottom to top, and at least part of the screw drills in the drill string assembly for under-reaming while drilling are single-bend screw drills, solving the technical problems of narrow clearance and narrow safety pressure window existing in drilling of difficult-to-drill formations in deep wells.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield drilling engineering, and particularly to a deep well drilling method. Background Art

[0002] With the continuous advancement of oil and gas exploration and development towards deeper layers, deep well drilling will face a series of engineering problems brought about by more complex formation pressure systems and lithologies, as well as extreme formation temperatures, pressures, stresses and other environments. Due to the complex structure, there are situations such as the superposition of three-phase detachment faults, high steepness, strong in-situ stress, and many fractures. The understanding of the properties and mechanical behaviors of ultra-deep rocks is limited, and their rock mechanics constitutive relations may be significantly different from those of shallow layers. The unclear deep geological mechanics mechanism will lead to the lack of scientific basis for engineering scheme design and construction optimization, resulting in the situation that the wellbore structure system may not meet the requirements of future ultra-deep well drilling due to insufficient safety margins during actual drilling. Summary of the Invention

[0003] The purpose of the present invention is to provide a deep well drilling method to solve the technical problems of narrow gaps and narrow safety pressure windows existing in drilling difficult-to-drill formations in deep wells.

[0004] The above object of the present invention can be achieved by the following technical solutions:

[0005] The present invention provides a deep well drilling method, including:

[0006] Drill the upper formation to a preset formation depth and perform cementing;

[0007] Perform under-reaming while drilling the lower formation and perform cementing;

[0008] Drill and cement the remaining formation;

[0009] The performing under-reaming while drilling the lower formation includes: performing N trips of drilling using a bottom-hole assembly for under-reaming while drilling; the bottom-hole assembly for under-reaming while drilling includes a PDC bit, a screw drill, and an under-reamer arranged from bottom to top, and at least part of the screws in the bottom-hole assembly for under-reaming while drilling are single-bend screws.

[0010] In a preferred embodiment, the bottom-hole assembly for under-reaming while drilling used for the N trips of drilling includes: a first bottom-hole assembly used first and a second bottom-hole assembly used subsequently; the PDC bit in the first bottom-hole assembly uses double-row teeth arrangement; the PDC bit in the second bottom-hole assembly uses a 2-blade 2-cone composite bit.

[0011] In a preferred embodiment, the drill string assembly of the underreamer while drilling used in the N trips of drilling includes a third drill string assembly used after the second drill string assembly, and the PDC bit in the third drill string assembly is a six-blade double-row tooth bit or a six-blade non-planar tooth bit.

[0012] In a preferred embodiment, the third drill string assembly includes, in sequential connection, the PDC bit, the screw drill, the non-magnetic drill collar, the centralizer, the drill collar, the underreamer, the spiral drill collar, the downhole shock absorber, the heavy drill pipe, the underreamer, and the drill pipe.

[0013] In a preferred embodiment, the second drill string assembly includes, in sequential connection, the PDC bit, the screw drill, the non-magnetic drill collar, the centralizer, the drill collar, the downhole shock absorber, the heavy drill pipe, the underreamer, and the drill pipe; the screw drill is a single-bend screw drill.

[0014] In a preferred embodiment, the first drill string assembly includes, in sequential connection, the PDC bit, the screw drill, the non-magnetic drill collar, the centralizer, the drill collar, the downhole shock absorber, the heavy drill pipe, the underreamer, and the drill pipe; the screw drill is a single-bend screw drill.

[0015] In a preferred embodiment, the underreamer includes a first blade and a second blade, the first blade is located above the second blade, and both the first blade and the second blade are spiral-shaped.

[0016] In a preferred embodiment, the spiral directions of the first blade and the second blade are opposite, and the roots of the first blade and the second blade are arranged away from each other.

[0017] In a preferred embodiment, the number of drilling intervals in the lower formation is M, M≥5, and N≥3.

[0018] In a preferred embodiment, the single-bend screw drill is a screw drill with a 1.25° bend angle.

[0019] The features and advantages of the present invention are as follows:

[0020] This deep well drilling method fully considers the characteristics of difficult-to-drill formations in deep wells. Through the drill string assembly of the underreamer while drilling, the size of the lower wellbore is adjusted in a timely manner, effectively solving the problems of narrow annulus and narrow safety pressure window. While achieving drilling speed increase in the difficult-to-drill formations of deep wells, the annulus clearance is increased, ensuring the safe running-in of the lower casing and improving the cementing quality. Description of the Drawings

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0022] Figure 1 Schematic diagram of the deep well drilling method provided by the present invention;

[0023] Figure 2 Schematic diagram of an embodiment of the drill string combination for under-reaming while drilling in the deep well drilling method provided by the present invention;

[0024] Figure 3 For Figure 2 Partial enlarged view at A in

[0025] Figure 4 For Figure 2 Partial enlarged view at B in

[0026] Figure 5 Schematic diagram of the structure of an embodiment of the six-opening wellbore constructed by the deep well drilling method provided by the present invention.

[0027] Explanation of the reference numerals in the drawings:

[0028] 1. Bit;

[0029] 2. Screw pump; 20. Bent screw pump; 21. Threaded joint;

[0030] 3. Non-magnetic drill collar; 4. Centralizer; 5. Drill collar; 6. Downhole shock absorber; 7. Heavy drill pipe;

[0031] 8. Under-reamer; 81. First cutting blade; 82. Second cutting blade;

[0032] 9. Drill pipe;

[0033] 101. First-opening wellbore structure; 102. Second-opening wellbore structure; 103. Third-opening wellbore structure; 104. Fourth-opening wellbore structure; 105. Fifth-opening wellbore structure; 106. Sixth-opening wellbore structure;

[0034] 111. Fourth-opening tie-back casing; 112. Fifth-opening tie-back casing. Detailed implementation manners

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] The present invention provides a deep well drilling method, as Figure 1 shown, including:

[0037] Step S10, drilling the upper formation to a preset formation depth and performing cementing;

[0038] Step S20, performing under-reaming while drilling the lower formation and performing cementing;

[0039] Step S30, drilling and cementing the remaining formation.

[0040] Performing under-reaming while drilling the lower formation includes: using the drill string assembly for under-reaming while drilling to drill N trips; the drill string assembly for under-reaming while drilling includes a PDC bit, a screw 2, and an under-reamer 8 arranged from bottom to top, and at least part of the screws 2 in the drill string for under-reaming while drilling are single-bend screws 2.

[0041] The single-bend screw 2 drives the bit 1 to rotate. Since the single-bend screw 2 has a bend angle, eccentricity will occur during rotation to ream the wellbore; subsequently, the under-reamer 8 corrects the wellbore wall. This deep well drilling method fully considers the characteristics of difficult-to-drill formations in deep wells. Through the drill string assembly for under-reaming while drilling, the size of the lower wellbore is adjusted in a timely manner, effectively solving the problems of narrow annulus and narrow safety pressure window. While achieving drilling speed increase in difficult-to-drill formations in deep wells, the annulus clearance is increased, ensuring the safe running-in of the lower casing and improving the cementing quality.

[0042] Specifically, in step S10, the upper formation is drilled to the preset formation depth according to the original designed wellbore structure and cementing operations are performed. Since the deep geological mechanics mechanism is not clear, combined with the comprehensive analysis of the characteristics of the uncovered formations, in order to avoid complex accidents and improve the cementing quality, it is necessary to perform reaming operations on the engineering scheme design and construction of the lower deep difficult-to-drill formations. Through step S20, the drill string assembly for under-reaming while drilling is used to perform under-reaming while drilling on the deep difficult-to-drill formations.

[0043] The drill string assembly for under-reaming while drilling used for N trips includes: the first drill string assembly used first and the second drill string assembly used subsequently. The structure of the first drill string assembly and the structure of the second drill string assembly may be the same or different.

[0044] The drill bit 1 can be a roller cone bit, a PDC bit or a composite bit. The drill bit 1 adopts a matrix PDC bit with a high tooth density and strong impact resistance and abrasion resistance, and is combined with a drilling parameter optimization system to increase the speed.

[0045] Furthermore, the structure of the first drill string assembly is different from that of the second drill string assembly. The PDC bit in the first drill string assembly uses double-row tooth arrangement; the PDC bit in the second drill string assembly uses a 2-blade 2-roller cone composite bit. Further still, the drill string assembly for underreaming while drilling used in N trips of drilling includes a third drill string assembly used after the second drill string assembly. The PDC bit in the third drill string assembly uses a six-blade double-row tooth bit or a six-blade non-planar tooth bit.

[0046] Considering the characteristics of deep well and difficult-to-drill formations, in order to improve the safety of drilling and the cementing quality, the inventor continued to make improvements: The third drill string assembly includes a PDC bit, a screw drill 2, a non-magnetic drill collar 3, a centralizer 4, a drill collar 5, an underreamer 8, a spiral drill collar 5, a downhole shock absorber 6, a heavy drill pipe 7, an underreamer 8 and a drill pipe 9 connected in sequence. The screw drill 2 in the third drill string assembly can be an ordinary screw drill 2, that is, without a bend.

[0047] Furthermore, the second drill string assembly includes a PDC bit, a screw drill 2, a non-magnetic drill collar 3, a centralizer 4, a drill collar 5, a downhole shock absorber 6, a heavy drill pipe 7, an underreamer 8 and a drill pipe 9 connected in sequence; the screw drill 2 in the second drill string assembly is a single-bend screw drill 2. The first drill string assembly includes a PDC bit, a screw drill 2, a non-magnetic drill collar 3, a centralizer 4, a drill collar 5, a downhole shock absorber 6, a heavy drill pipe 7, an underreamer 8 and a drill pipe 9 connected in sequence; the screw drill 2 in the first drill string assembly is a single-bend screw drill 2.

[0048] In one embodiment, the underreamer 8 includes a first blade 81 and a second blade 82. The first blade 81 is located above the second blade 82, and both the first blade 81 and the second blade 82 are spiral-shaped. A plurality of first blades 81 are arranged in groups, and the plurality of first blades 81 in the same group are circumferentially distributed around the main body of the underreamer 8. A plurality of second blades 82 are arranged in groups, and the plurality of second blades 82 in the same group are circumferentially distributed around the main body of the underreamer 8. Further, the spiral directions of the first blade 81 and the second blade 82 are opposite, and the roots of the first blade 81 and the second blade 82 are arranged away from each other. As Figures 2 - 4 shown, the first blade 81 and the second blade 82 are in one-to-one correspondence, and the corresponding first blade 81 and second blade 82 are integrally V-shaped. More preferably, the corresponding first blade 81 and second blade 82 are symmetrical.

[0049] Both the first blade 81 and the second blade 82 adopt a micro-eccentric structure design.

[0050] The first blade 81 and the second blade 82 in the micro reamer 8 play the roles of reaming and centralizing, can perform reaming during drilling to eliminate irregular wellbores and ensure the smoothness of the wellbore. PDC cutting teeth and gauge composite inserts can be installed on the first blade 81 and the second blade 82.

[0051] In one embodiment, the number of drilling intervals in the lower formation is M, M≥5, N≥3. For example: The wellbore drilled by this deep well drilling method has a total of six drilling intervals. The upper formation includes the wellbore of four drilling intervals, the lower formation is the wellbore of the fifth drilling interval, and the remaining formation is the wellbore of the sixth drilling interval.

[0052] Further, the single bend screw 2 is a screw 2 with a bend angle of 1.25°. The single bend screw 2 includes a threaded joint 21, and the threaded joint 21 is preferably an internal thread connection end.

[0053] For ease of understanding, the following is described by way of an example.

[0054] Figure 5 The wellbore structure is shown. Among them, the first open wellbore structure 101 is a Φ914.4mm drill hole and a Φ720mm casing is run in for 30m; the second open wellbore structure 102 is a Φ660.4mm wellbore and a Φ508mm casing is run in for 698m; the third open wellbore structure 103 is a Φ455mm wellbore and a Φ374.65mm casing is run in for 2738m; the fourth open wellbore structure 104 is a Φ333.4mm wellbore and a Φ282.58mm hanger casing is run in for (2588 - 5893)m, and the tie-back casing is 286.58×2588m; the fifth open wellbore structure 105 is a Φ241.3mm wellbore and a Φ206.38mm hanger casing is run in for (5493 - 7441)m, and the tie-back casing is Φ206.38mm×5493m; the sixth open wellbore structure 106 is a Φ165.1mm wellbore and a Φ139.7mm casing is run in.

[0055] During drilling, after drilling to the fourth open and completing cementing, usually, for the fifth open wellbore with a diameter of φ241.3mm, a φ206.38mm casing 14 is run in. The unilateral annulus clearance is 17.46mm, and the minimum clearance at the collar position is 9.65mm. Considering the geological conditions, there are problems of narrow clearance and narrow safety pressure window, which are likely to induce leakage and it is difficult to ensure the cementing quality.

[0056] Using the deep well drilling method proposed by the present invention for reaming operation, the well diameter can be expanded from Φ241.3mm to 254mm, which can improve the equivalent circulating density (ECD) of the drilling fluid and provide necessary guarantee for the cementing quality. The specific steps include:

[0057] For the first and second runs of drilling, use the first drill string assembly. The first drill string assembly includes: a Φ241.3mm PDC bit + a screw drill 2 (with a 1.25° bend angle) + three Φ165.1mm non-magnetic drill collars + a Φ240mm centralizer 4 + five Φ165.1mm drill collars + a Φ165mm downhole shock absorber 6 + seven Φ127mm heavyweight drill pipes + an 8-Φ230mm underreamer + nine Φ139.7mm drill pipes. Among them, the screw drill 2 is a Φ197mm screw drill 2 and is a bent screw drill 20 with a 1.25° bend angle; the Φ127mm heavyweight drill pipes 7 are 20 - 40 in number.

[0058] The underreamer 8 mainly functions to correct the wellbore and effectively perform underreaming operations on the wellbore of the current size; the bit 1 uses a matrix PDC bit with a high tooth density, strong impact resistance, and strong abrasion resistance, and is combined with a drilling parameter optimization system to increase the drilling speed. The bit 1 adopts: a matrix bit + gauge protection to improve the stability and abrasion resistance of the bit 1; double-row tooth arrangement, 16mm teeth, to improve the stability of the bit 1; special-shaped teeth to improve the aggressiveness.

[0059] The drilling parameters include: a weight on bit of 120 - 180kN; a rotary speed of 70 - 80rpm, and downhole power tools are used; a flow rate of 28 - 35L / s; and a pump pressure of 28 - 32MPa.

[0060] For the third run of drilling, use the second drill string assembly. The second drill string assembly includes: a Φ241.3mm PDC bit + a screw drill 2 + three Φ165.1mm non-magnetic drill collars + a Φ240mm centralizer 4 + five Φ165.1mm drill collars + a Φ165mm downhole shock absorber 6 + seven Φ127mm heavyweight drill pipes + an 8-Φ230mm underreamer + nine Φ139.7mm drill pipes. Among them, the screw drill 2 is a Φ197mm screw drill 2 and is a bent screw drill 20 with a 1.25° bend angle; the Φ127mm heavyweight drill pipes 7 are 20 - 40 in number. The bit 1 adopts: a two-cone two-cone composite bit.

[0061] The drilling parameters include: a weight on bit of 120 - 180kN; a rotary speed of 70 - 80rpm, and downhole power tools are used; a flow rate of 28 - 35L / s; and a pump pressure of 28 - 32MPa.

[0062] For the fourth and fifth runs of drilling, use the third drill string assembly. The third drill string assembly includes: a Φ241.3mm PDC bit + a Φ197mm screw drill 2 + three Φ165.1mm non-magnetic drill collars + a Φ240mm centralizer 4 + five Φ165.1mm drill collars + an 8-Φ230mm underreamer + five Φ165.1mm spiral drill collars + a 66-Φ165mm downhole shock absorber + seven Φ127mm heavyweight drill pipes + an 8-Φ230mm underreamer + nine Φ139.7mm drill pipes. Among them, the Φ127mm heavyweight drill pipes 7 are 20 - 40 in number; the bit 1 adopts: a six-cone double-row tooth bit or a six-cone non-planar tooth bit.

[0063] The drilling parameters include: the weight on bit is 120 - 180 kN; the rotary speed is 70 - 80 rpm, and downhole power tools are used; the displacement is 28 - 35 L / s; the pump pressure is 28 - 32 MPa.

[0064] The deep well drilling method proposed by the present invention fully considers the characteristics of difficult - to - drill formations in deep wells. By using a drill string assembly for under - reaming while drilling in difficult - to - drill formations in deep wells, the size of the lower wellbore and the wellbore structure are adjusted. The expected hole enlargement rate is 8 - 10%, effectively solving the problems of narrow annulus and easy loss of circulation, providing necessary wellbore conditions for the cementing quality, and reducing the accident complexity rate.

[0065] The following table is a comparison table of the drill string assembly scheme in the present invention and the original scheme.

[0066]

[0067] As can be seen from the above table, the drilling method of the present invention can reduce the number of bits and screws used, increase the penetration rate, shorten the drilling cycle, improve the equivalent circulating density (ECD), and ensure the cementing quality.

[0068] The above are only several embodiments of the present invention. Those skilled in the art can make various changes or modifications to the embodiments of the present invention without departing from the spirit and scope of the present invention based on the content disclosed in the application documents.

Claims

1. A deep well drilling method, characterized in that, it includes: Drill the upper formation to a preset formation depth and perform cementing; Perform under-reaming while drilling the lower formation and perform cementing; Drill and perform cementing on the remaining formation; The under-reaming while drilling the lower formation includes: using the drill string assembly for under-reaming while drilling to drill N trips; the drill string assembly for under-reaming while drilling includes a PDC bit, a screw drill, and an under-reamer arranged from bottom to top, and at least part of the screw drill in the drill string for under-reaming while drilling is a single-bend screw drill; The drill string assembly for under-reaming while drilling used for the N trips includes: the first drill string assembly used first and the second drill string assembly used subsequently; The PDC bit in the first drill string assembly uses double-row arranged teeth; the PDC bit in the second drill string assembly uses a 2-blade 2-cone composite bit; The drill string assembly for under-reaming while drilling used for the N trips includes a third drill string assembly used after the second drill string assembly, and the PDC bit in the third drill string assembly uses a six-blade double-row tooth bit or a six-blade non-planar tooth bit.

2. The deep well drilling method according to claim 1, characterized in that, The third drill string assembly includes the PDC bit, the screw drill, a non-magnetic drill collar, a centralizer, a drill collar, the under-reamer, a spiral drill collar, a downhole shock absorber, a heavy drill pipe, the under-reamer, and a drill pipe connected in sequence.

3. The deep well drilling method according to claim 1, characterized in that, The second drill string assembly includes the PDC bit, the screw drill, a non-magnetic drill collar, a centralizer, a drill collar, a downhole shock absorber, a heavy drill pipe, the under-reamer, and a drill pipe connected in sequence; The screw drill is a single-bend screw drill.

4. The deep well drilling method according to claim 1, characterized in that, The first drill string assembly includes the PDC bit, the screw drill, a non-magnetic drill collar, a centralizer, a drill collar, a downhole shock absorber, a heavy drill pipe, the under-reamer, and a drill pipe connected in sequence; The screw drill is a single-bend screw drill.

5. The deep well drilling method according to claim 1, characterized in that, The under-reamer includes a first blade and a second blade, the first blade is located above the second blade, and both the first blade and the second blade are spiral-shaped.

6. The deep well drilling method according to claim 5, characterized in that, The spiral directions of the first blade and the second blade are opposite, and the roots of the first blade and the second blade are arranged away from each other.

7. The deep well drilling method according to claim 1, characterized in that, The number of drilling intervals of the lower formation is M, M≥5, N≥3.

8. The deep well drilling method according to any one of claims 1-7, characterized in that, The single-bend screw drill is a screw drill with a 1.25° bend angle.

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