An experimental method suitable for hydraulic parameter design of jet drilling

Abstract

The present invention relates to the fields of oil and gas drilling, geological exploration, and mining drilling technology, and particularly to an experimental method suitable for designing hydraulic parameters for jet drilling. The method comprises: obtaining basic parameters for jet drilling of a formation to be drilled; conducting an indoor experiment on threshold jet pressure using rocks to simulate different confining pressure conditions underground; plotting and fitting a curve showing the variation of threshold jet pressure with confining pressure to obtain a formula for calculating the threshold jet pressure when jet damage occurs in the formation to be drilled under any confining pressure; calculating the minimum surface pump pressure required for jet drilling of the formation to be drilled at different well depths; comparing the minimum surface pump pressure required for jet drilling of the formation to be drilled with the rated pump pressure of the drilling pump to determine whether the formation to be drilled is suitable for jet drilling; and designing hydraulic parameters for jet drilling under existing pump conditions. The method provides guidance for the design and construction of jet drilling.

Description

Technical Field

[0001] The present invention relates to the technical fields of oil and gas drilling, geological exploration and mine drilling, and in particular to an experimental method suitable for designing hydraulic parameters of jet drilling. Background Art

[0002] High-pressure jet drilling utilizes the hydraulic action of high-speed jets of drilling fluid passing through the drill bit nozzle to clean the wellbore, assist the drill bit in breaking rock, and thereby increase the rate of penetration (ROP). Since its introduction in the 1960s, it has been extensively tested and studied in numerous oil and gas fields both domestically and internationally, achieving breakthroughs in improving wellbore cleansing capabilities, increasing drill bit footage, and increasing ROP. This opens up broad prospects and potential for future development in the efficient and rapid drilling of complex deep wells.

[0003] A large number of studies and practices have shown that the higher the jet rate of high-pressure jet drilling, the greater the mechanical penetration rate and the greater the drill bit footage. However, during field application, there are inevitably some difficult-to-solve technical problems: using ground equipment to generate high pressure and transmit it to the bottom of the well requires a large amount of capital to add or replace a series of complex equipment and wearing parts, and compared with conventional drilling equipment, its performance and installation, disassembly, and maintenance requirements are much higher; in addition, affected by the performance factors of diesel engines, drilling pumps, and drilling fluids, jet drilling cannot maintain high pump pressure for a long time. Continuous high pump pressure for a long time can easily lead to damage to the diesel engine and drilling pump, as well as high-pressure pipelines, faucet flushing and drill string leakage, thereby increasing ground repair time and the probability of downhole accidents.

[0004] The paper "35MPa High-Pressure Jet Drilling Technology Practice" published in November 2012 in Petroleum Drilling Technology focuses on the upgrade and transformation of the 70D drilling rig power and circulation system to meet the safety requirements of 35MPa high-pressure jet drilling, and carries out the technical practice of high-pressure jet drilling based on the hydraulic parameter design ideas of large displacement and appropriate drill bit pressure drop. After analysis, the application ideas of jet drilling technology mentioned in the paper have the following shortcomings: (1) To implement jet drilling, the upgrade and transformation of the drilling rig power and circulation system to meet the pump pressure requirements of 35MPa or even higher will lead to a large increase in capital costs; (2) Although the high-pressure jet drilling construction of about 35MPa is carried out in different regions and different formations, it is easy to cause a great waste of hydraulic energy during the jetting of some formations; (3) Considering the high cost of supporting and transformation of high-pressure jet drilling equipment and the potential safety hazards of high-pressure jet drilling on the ground and underground, the technical adaptability and promotion and application prospects of high-pressure jet drilling are seriously restricted.

[0005] The June 1998 publication of Petroleum Drilling Technology, "Optimal Hydraulic Design and Analysis of Small-hole Wells," fully considers the characteristics of small-hole drilling and rationally determines annular pressure loss. By organically combining jet drilling and annular rock-carrying, it proposes a theoretical method for hydraulic parameter design for small-hole drilling under two operating modes: maximum water power and maximum impact force. While the hydraulic parameter design method described in this paper takes into account the operating capacity of existing pumps, it fails to consider the adaptability of jet drilling in different formations, nor the impact of wellbore annular pressure on rock strength and the difficulty of jet drilling. Consequently, the hydraulic parameters optimized using this method may not meet the requirements for hydraulic jet rock breaking.

[0006] In summary, existing technologies cannot use experimental methods to conduct in-depth evaluation of the formation adaptability of jet drilling, nor can they combine the capacity conditions of on-site drilling pumps and high-pressure pipeline equipment to provide guidance for the design and construction of future on-site high-pressure jet drilling. Summary of the Invention

[0007] The purpose of the present invention is to provide an experimental method suitable for the design of hydraulic parameters of jet drilling in view of the deficiencies in the prior art.

[0008] By using cores from adjacent wells or outcrop rocks in the block to conduct threshold jet pressure experiments simulating different confining pressure conditions downhole, the optimal hydraulic parameters for jet drilling under existing machine pump conditions are obtained. Combined with the capacity conditions of on-site drilling pumps and high-pressure pipeline equipment, guidance is provided for the design and construction of future jet drilling.

[0009] The technical solution is as follows:

[0010] An experimental method suitable for designing hydraulic parameters of jet drilling comprises the following steps:

[0011] Step (1) obtaining basic parameters of jet drilling of the formation to be drilled;

[0012] Step (2) using cores from adjacent wells or outcrop rocks from the block to make standard cylindrical specimens, and conducting indoor experiments on threshold jet pressures simulating different confining pressure conditions downhole;

[0013] Step (3) draw and fit the curve of the change law of threshold jet pressure with confining pressure to obtain the threshold jet pressure P when jet destruction occurs in the formation to be drilled under any confining pressure cr (p) calculation formula;

[0014] Step (4) Calculate the minimum surface pump pressure P required for jet drilling in the formation to be drilled at different well depths smin size;

[0015] Step (5) Comparing the minimum surface pump pressure P required for jet drilling in the formation to be drilled sminand drilling pump rated pump pressure P r , judge whether the formation to be drilled is suitable for jet drilling:

[0016] If P smin >P r , then the existing pump conditions are not suitable for jet drilling;

[0017] If P smin ≤P r , indicating that jet drilling can be implemented;

[0018] Step (six) Design the hydraulic parameters of jet drilling under the existing pump conditions to obtain the optimal drilling fluid displacement Q for jet drilling in the formation to be drilled under the existing pump conditions. opt , optimal nozzle diameter d e And the maximum jet drilling depth H max .

[0019] The technical solution of the present invention further includes:

[0020] The basic parameters of jet drilling in the formation to be drilled in step (1) include drilling fluid density, drilling fluid viscosity, wellbore structure, drill bit assembly and wellbore expansion rate, which are mainly obtained based on drilling design data and actual drilling data of adjacent wells.

[0021] The minimum surface pump pressure P required for jet drilling in the formation to be drilled at different well depths in step (4) smin To use the minimum drilling fluid displacement Q a The pump pressure at time , can be obtained by equations (1) to (11):

[0022] P smin =ΔP b +ΔP g +ΔP p +ΔP c (1)

[0023] ΔP b =P cr (p) (2)

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033] When designing the hydraulic parameters of jet drilling under the existing pump conditions in step (six), the optimal drilling fluid displacement Q for jet drilling in the formation to be drilled under the existing pump conditions is opt , optimal nozzle diameter d e Obtained by formula (12) formula (13) or formula (14) formula (15):

[0034] 1. When P cr (p)≤0.643P r hour

[0035]

[0036]

[0037] 2. When P cr (p)>0.643P r hour

[0038]

[0039]

[0040] Among them, C is the drill nozzle flow coefficient, which is related to the nozzle resistance coefficient.

[0041] The maximum jet drilling depth H of the formation to be drilled under the existing pump conditions max Obtained from formula (16):

[0042]

[0043] In the above formula, ΔP b is the drill bit pressure drop during jet drilling; ΔP g , ΔP p and ΔP c are the circulating pressure losses inside and outside the surface manifold, drill pipe, and drill collar respectively; K g , K p , K c They are the pressure loss coefficients of the surface manifold, the inside and outside of the drill pipe, and the inside and outside of the drill collar; L1, L2, L3, L4 and L p 、L c are the lengths of the surface high-pressure pipeline, riser, hose, kelly, downhole drill pipe, and drill collar respectively; d1, d2, d3, d4 and d pi d ciThey are the inner diameters of surface high-pressure pipelines, risers, hoses, kellys, downhole drill pipes, and drill collars; d p d c are the outer diameters of the drill pipe and drill collar respectively; d h is the wellbore diameter after considering the wellbore expansion rate; ρ d 、μ pv are the density and plastic viscosity of the drilling fluid respectively; v a is the minimum return velocity in the wellbore annulus; p is the bottomhole confining pressure at different well depths in the formation to be drilled; C is the drill bit nozzle flow coefficient, which is related to the nozzle resistance coefficient.

[0044] The beneficial effects of the present invention are:

[0045] (1) The experimental method of the present invention can use experimental means to conduct an in-depth evaluation of the formation adaptability for jet drilling. It can not only determine whether the formation to be drilled is suitable for jet drilling under the existing machine pump conditions, but also guide the optimization design of hydraulic parameters for jet drilling of the formation to be drilled.

[0046] (2) The experimental method of the present invention is simple in calculation, accurate and reliable, and is easy to use by on-site technicians. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The figure is a flow chart of the experimental method for hydraulic parameter design of jet drilling according to the present invention.

[0048] Figure 2 This is a schematic diagram of a fitting curve showing the variation of the threshold jet pressure with the confining pressure in the experimental method for the design of hydraulic parameters for jet drilling according to the present invention. DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] Refer to the instruction manual Figure 1 and 2 The present invention provides an experimental method for designing hydraulic parameters of jet drilling, which mainly includes the following steps:

[0051] Step 1: Obtaining basic parameters of jet drilling in the formation to be drilled

[0052] Collect the engineering design data of the current well and the actual drilling data of adjacent wells to obtain the basic parameters of jet drilling in the formation to be drilled, mainly including drilling fluid density, drilling fluid viscosity, wellbore structure, drill tool combination and wellbore expansion rate, which are mainly obtained based on the drilling design data and the actual drilling data of adjacent wells.

[0053] Step (2) Conducting indoor experiments on threshold jet pressure simulating different confining pressure conditions downhole

[0054] Collect core data from adjacent wells or outcrop rocks in the sampling block, use coring drill tools to produce cylindrical samples with a diameter of ≥10cm and a length of 15-20cm, and carry out more than three sets of threshold jet pressure experiments simulating different confining pressure conditions underground on a surface high-pressure pump.

[0055] Step (3) Draw the curve of the change of threshold jet pressure with the surrounding pressure, and fit it to obtain the calculation formula of threshold jet pressure

[0056] Draw the curve of the change of threshold jet pressure with the surrounding pressure and fit it, refer to the attached Figure 2 , and then the threshold jet pressure P when jet destruction occurs in the formation to be drilled under any confining pressure can be obtained cr (p)Calculation formula.

[0057] Step 4: Calculate the minimum surface pump pressure required for jet drilling in the formation to be drilled

[0058] The minimum surface pump pressure P required for jet drilling in the formation to be drilled at different well depths smin To use the minimum drilling fluid displacement Q a The pump pressure at time , can be obtained by equations (1) to (16):

[0059] P smin =ΔP b +ΔP g +ΔP p +ΔP c (1)

[0060] ΔP b =P cr (p) (2)

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070] Step 5: Determine whether the formation to be drilled is suitable for jet drilling

[0071] Comparison of the minimum surface pump pressure P for jet drilling in the formation to be drilled smin and drilling pump rated pump pressure P r , judge whether the formation to be drilled is suitable for jet drilling:

[0072] If P smin >P r , then the existing pump conditions are not suitable for jet drilling;

[0073] If P smin ≤P r , indicating that jet drilling can be implemented.

[0074] Step 6: Design hydraulic parameters of jet drilling under existing pump conditions

[0075] The optimal drilling fluid displacement Q for jet drilling in the formation to be drilled under existing pump conditions opt , optimal nozzle diameter d ε Obtained by formula (12) formula (13) or formula (14) formula (15):

[0076] 1. When P cr (p)≤0.643P r hour

[0077]

[0078]

[0079] 2. When P cr (p)>0.643P r hour

[0080]

[0081]

[0082] In addition, the maximum jet drilling depth H of the formation to be drilled under the existing pump conditions can be obtained. max for:

[0083]

[0084] Explanation of formula symbols: In formula (1) to formula (16), ΔP b is the drill bit pressure drop during jet drilling; ΔP g , ΔP p and ΔP c are the circulating pressure losses inside and outside the surface manifold, drill pipe, and drill collar respectively; K g , K p , Kc They are the pressure loss coefficients of the surface manifold, the inside and outside of the drill pipe, and the inside and outside of the drill collar; L1, L2, L3, L4 and L p 、L c are the lengths of the surface high-pressure pipeline, riser, hose, kelly, downhole drill pipe, and drill collar respectively; d1, d2, d3, d4 and d pi d ci They are the inner diameters of surface high-pressure pipelines, risers, hoses, kellys, downhole drill pipes, and drill collars; d p d c are the outer diameters of the drill pipe and drill collar respectively; d h is the wellbore diameter after considering the wellbore expansion rate; ρ d 、μ pv are the density and plastic viscosity of the drilling fluid respectively; v a is the minimum return velocity in the wellbore annulus; p is the bottomhole confining pressure at different well depths in the formation to be drilled; C is the drill bit nozzle flow coefficient, which is related to the nozzle resistance coefficient.

[0085] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. An experimental method suitable for designing hydraulic parameters of jet drilling, characterized by: The following steps are involved: Step (1) obtaining basic parameters of jet drilling of the formation to be drilled; Step (2) using cores from adjacent wells or outcrop rocks from the block to make standard cylindrical specimens, and conducting indoor experiments on threshold jet pressures under simulated downhole confining pressures; Step (3) draw and fit the curve of the change law of threshold jet pressure with confining pressure to obtain the threshold jet pressure P when jet destruction occurs in the formation to be drilled under any confining pressure cr (p) calculation formula; Step (4) Calculate the minimum surface pump pressure P required for jet drilling in the formation to be drilled at different well depths smin size; Step (5) Comparing the minimum surface pump pressure P required for jet drilling in the formation to be drilled smin and drilling pump rated pump pressure P r , to judge whether the formation to be drilled is suitable for jet drilling; Step (six) Design the hydraulic parameters of jet drilling under the existing pump conditions to obtain the drilling fluid displacement Q for jet drilling in the formation to be drilled under the existing pump conditions. opt , nozzle diameter d e The maximum jet drilling depth is H max ; The minimum surface pump pressure P required for jet drilling in the formation to be drilled at different well depths in step (4) smin To use the minimum drilling fluid displacement Q a The pump pressure at time , can be obtained by equations (1) to (11): P smin =ΔP b +ΔP g +ΔP p +ΔP c (1) ΔP b =P cr (p) (2) In the above formula, ΔP b is the drill bit pressure drop during jet drilling; ΔP g , ΔP p and ΔP c are the circulating pressure losses inside and outside the surface manifold, drill pipe, and drill collar respectively; K g , K p , K c They are the pressure loss coefficients of the surface manifold, the inside and outside of the drill pipe, and the inside and outside of the drill collar; L1, L2, L3, L4 and L p 、L c are the lengths of the surface high-pressure pipeline, riser, hose, kelly, downhole drill pipe, and drill collar respectively; d1, d2, d3, d4 and d pi d ci They are the inner diameters of surface high-pressure pipelines, risers, hoses, kellys, downhole drill pipes, and drill collars; d p d c are the outer diameters of the drill pipe and drill collar respectively; d h is the wellbore diameter after considering the wellbore expansion rate; ρ d 、μ pv are the density and plastic viscosity of the drilling fluid respectively; v a is the minimum return velocity in the wellbore annulus; p is the bottom hole confining pressure at different well depths in the formation to be drilled; The drilling fluid displacement Q of the jet drilling in the formation to be drilled under the existing pump conditions described in step (six) opt , nozzle diameter d e Obtained by formula (12) formula (13) or formula (14) formula (15): When P cr (p)≤0.643P r hour: When P cr (p)>0.643P r hour: Where C is the drill nozzle discharge coefficient; The maximum jet drilling depth H of the formation to be drilled under the existing pump conditions in step (six) max Obtained from formula (16):

2. The experimental method for designing hydraulic parameters of jet drilling according to claim 1, characterized in that: In step (5), determining whether the formation to be drilled is suitable for jet drilling includes: If P smin >P r , then the existing pump conditions are not suitable for jet drilling; If P smin ≤P r , indicating that jet drilling can be implemented.

3. The experimental method for designing hydraulic parameters of jet drilling according to claim 1, characterized in that: The basic parameters of the jet drilling of the formation to be drilled in step (1) include drilling fluid density, drilling fluid viscosity, wellbore structure, drill tool assembly and well diameter expansion rate.

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