Judgment method for borehole cleanliness

Abstract

The invention discloses a method for judging borehole cleanliness. The calculation formula of the borehole cleanliness K is as follows: # imgabs0 # alpha is a hole drift angle, D is the borehole diameter, V < return > is the volume of rock debris returned per unit length, and theta is the eccentricity of a power drilling tool. According to the method, the basic data of the volume of the well bottom return object is utilized, the influence of factors such as borehole diameter expansion and rock debris expansion caused by the hole deviation angle and the eccentricity of the drilling tool is comprehensively considered, the actual value is compared with the calculated amount in real time, operation is easy, meanwhile, errors are reduced, and the cleaning condition under the current borehole can be rapidly and accurately calculated; the defect that an existing model class calculation method is tedious is overcome.

Description

Technical Field

[0001] The invention relates to the technical field of oil well operation, and in particular to a method for determining the cleanliness of a wellbore. Background Art

[0002] During the drilling process, the issue of borehole cleanliness is one of the key factors affecting whether the drilling construction can proceed smoothly, especially for high-angle wells and horizontal wells. The uncleanness of the borehole will not only lead to slow drilling, resistance to drilling and electric measurement, but also cause the occurrence of drill bit jams in more serious cases, seriously affecting economic benefits. It can be seen that timely evaluation of the cleanliness of the borehole and taking different measures for the borehole according to the cleanliness are a major issue that needs to be studied in the current drilling operation.

[0003] The cleanliness of a wellbore is affected by various complex factors. Domestic and foreign scholars have conducted in-depth research on it. The method of calculating the cleanliness of a wellbore with high precision is relatively cumbersome, requiring professional personnel to use a matching software system for calculation, which is not convenient for on-site construction personnel to implement. For example, the patent document CN 113530525A records a method for analyzing the cleanliness of a wellbore, including: after determining the wellbore to be monitored, obtaining the historical drilling data of the wellbore to be monitored, and constructing a corresponding hook-loaded well depth modeling diagram according to a preset comprehensive friction coefficient scale and the historical drilling data of the wellbore to be monitored. According to the torque friction data actually measured at each target measurement site in the wellbore to be monitored, the actual measurement parameter points corresponding to each target measurement site are marked on the hook-loaded well depth modeling diagram. According to the standard friction coefficient curve, the actual friction coefficient corresponding to each actual measurement parameter point is determined. According to the actual friction coefficient of the current measurement site and the previous measurement site, the cleanliness of the wellbore to be monitored is determined. This method establishes multiple sets of models of key parameters, and determines the cleanliness of the wellbore by comparing the on-site actual drilling data with the model data. However, this process is complicated and time-consuming. Summary of the invention

[0004] The purpose of the present invention is to solve the above technical problems and provide a method for determining the cleanliness of a wellbore with simple calculation and high accuracy.

[0005] To achieve the above object, the present invention provides a method for determining the cleanliness of a wellbore. The calculation formula of the cleanliness K of the wellbore is as follows:

[0006]

[0007] α is the well inclination angle, D is the wellbore diameter, V 返 is the volume of returned cuttings per unit length, θ is the eccentricity of the power drill;

[0008] 1.5≤K≤2.5, continue drilling;

[0009] 1.1≤K<1.5, stop drilling and take measures to carry sand in circulation;

[0010] K<1.1, short start and down verification;

[0011] K>2.5, one cycle is repeated.

[0012] Furthermore, the specific process of K<1.1 and short trip verification is: if the short trip can be successfully carried out and the friction resistance is less than 10t, then circulate sand and carry it; if the trip encounters resistance and the eye is difficult, then the drill is pulled out and the drilling tool assembly is replaced to clear the well.

[0013] Furthermore, when K>2.5, the specific process of one cycle is as follows: if the shape of the returned cuttings is normal, the short trip is verified, and the short trip can be successfully completed, and the friction resistance is less than 5t, then drilling is resumed; if the returned cuttings are pieces of well wall peeling off, wellbore strengthening measures are taken to strengthen the well wall, the short trip is verified, and the short trip can be successfully completed, and the friction resistance is less than 5t, then drilling is resumed.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1) The present invention uses the basic data of the volume of the bottom return material, comprehensively considers the influence of factors such as the wellbore diameter expansion caused by the well inclination angle and the eccentricity of the drilling tool, and the expansion of the cuttings, and compares the actual and calculated amounts in real time. It is easy to operate and reduces errors. It can quickly and accurately calculate the cleaning situation under the current wellbore, overcoming the shortcomings of the cumbersome existing model-based calculation methods;

[0016] 2) The present invention can calculate and analyze the cleanliness of the wellbore in real time, grasp the cleanliness of the wellbore in real time, and take appropriate technical measures in time according to the cleanliness range to guide drilling production in real time. DETAILED DESCRIPTION

[0017] The present invention will be further described in detail below in conjunction with specific embodiments to facilitate a clearer understanding of the present invention, but they do not limit the present invention.

[0018] Based on the total amount of vibrating screen return, compared with the wellbore displacement volume, and taking into account the influence of factors such as cuttings settlement, wellbore expansion, and cuttings expansion, the calculation formula for wellbore cleanliness K is as follows:

[0019]

[0020] α is the well inclination angle, D is the wellbore diameter, V 返 is the volume of returned cuttings per unit length, θ is the eccentricity of the power drill;

[0021] 1.5≤K≤2.5, continue drilling;

[0022] 1.1≤K<1.5, stop drilling and take measures to carry sand in circulation;

[0023] K<1.1, short trip verification; if the short trip can be successfully carried out and the friction resistance is less than 10t, the sand carrying cycle is carried out; if the trip encounters resistance and the eye is difficult, the drill is pulled out and the drilling tool assembly is replaced to clear the well;

[0024] When K>2.5, repeat one cycle. If the shape of the returned cuttings is normal and the short trip is verified, and the short trip can be successfully completed with the friction resistance <5t, then resume drilling. If the returned cuttings are pieces of well wall peeling off, take wellbore strengthening measures to strengthen the well wall, and verify the short trip. If the short trip can be successfully completed with the friction resistance <5t, then resume drilling.

[0025] A well was drilled to a depth of 4562 meters, with an inclination angle of 82°, a wellbore diameter of 215.9 mm, and an eccentricity of 1.5° using a power drill.

[0026] Example 1

[0027] Place a cuttings tank at the outlet of the vibrating screen to collect the return material from the wellhead and measure the volume. The return material volume during drilling from 4552 to 4562 meters is 0.9 cubic meters, with an average return material of 0.09 cubic meters per meter. Substitute this into the formula to calculate the wellbore cleanliness K 4562 =2.08, the borehole cleanliness is within the normal range. The well also uses the DDI software of Huiyou Technology's downhole real-time intelligent monitoring system for tracking, calculation and evaluation. The system shows that the idling torque is 6.75-8.23 kN·m, the instantaneous starting torque of the top drive is 10.2-10.65 kN·m, the actual drilling torque is 8-12.5 kN·m, the drilling torque is 13-5 kN·m in the idling torque additional value, the instantaneous starting torque is less than 15 kN·m, and the wellhead returns quickly when the pump is turned on, and the pump pressure increases evenly with the displacement, indicating that the downhole situation is normal, the well wall is stable, and the wellbore cleanliness is high.

[0028] Example 2

[0029] The well was drilled to 5022 meters, with a well inclination of 91°, a wellbore diameter of 215.9 mm, and a power drill with an eccentricity of 1.5°. The return volume during drilling from 5017 to 5022 meters was 0.22 cubic meters, with an average return volume of 0.044 cubic meters per meter. The wellbore cleanliness K was calculated by substituting it into the formula. 5022 =0.996, requiring short trip verification. However, in order to meet the deadline, the site did not conduct a short trip verification in time, nor did it take sand-carrying measures. The drilling continued until 5030 meters, when the pump was blocked and the top drive was stuck. It was difficult to pull the drill back, so the drill was later pulled to replace the well drilling tool assembly for well clearance treatment.

[0030] Example 3

[0031] A well was drilled to a depth of 3400 meters, with a well inclination of 64° and a borehole diameter of 311.2 mm. The eccentricity of the power drill was 1.0°. The return volume was 0.4 cubic meters when drilling from 3396 to 3400 meters, with an average return volume of 0.1 cubic meters per meter. Substitute this into the formula to calculate the wellbore cleanliness K 3400 =1.2, according to the wellbore cleanliness 1.1≤K<1.5, it is necessary to stop drilling and take measures to carry sand in circulation. Considering that there is no abnormality in the construction parameters, the drilling team continued drilling. When drilling to 3416 meters, the pump was blocked. The annulus was not smooth when the pump was turned on again. A small displacement was adopted to establish circulation, and the displacement was gradually increased to carry sand in circulation. 2.4 cubic meters of sediment were returned. After a short start to the vertical well section, the well was drilled down and the drilling was resumed.

[0032] Example 4

[0033] A well was drilled to a depth of 6311 meters, with a well inclination of 90°, a borehole diameter of 149.2 mm, and a power drill with an eccentricity of 1.0°. The return volume during the drilling of 6301-6311 meters was 0.67 cubic meters, with an average return volume of 0.067 cubic meters per meter. Substitute this into the formula to calculate the wellbore cleanliness K 3400 =3.2, the drilling team stopped drilling, slowly reversed the eyelet circulation (friction resistance 25 tons, torque 15 kN·m), observed the sand return of the vibrating screen, and found that the returned materials were all formation blocks, and the returned amount continued to increase. The drilling fluid performance was immediately adjusted on site to enhance the anti-collapse inhibition. At the same time, the drilling fluid density was increased by 0.03 g / cubic centimeter and continued to circulate until there was no block returned from the wellhead. After a short trip and verification, the friction resistance was 3 tons, and drilling was resumed.

Claims

1. A method for determining the cleanliness of a wellbore, characterized in that: The calculation formula of wellbore cleanliness K is as follows: α is the well inclination angle, D is the wellbore diameter, V 返 is the volume of returned cuttings per unit length, θ is the eccentricity of the power drill; 1.5≤K≤2.5, continue drilling; 1.1≤K<1.5, stop drilling and take measures to carry sand in circulation; K<1.1, short start and down verification; K>2.5, one cycle is repeated.

2. The method for determining the cleanliness of a wellbore according to claim 1, characterized in that: The specific process of the K<1.1, short trip verification is: if the short trip can be successfully carried out and the friction resistance is less than 10t, the sand is carried out in a cycle; if the trip encounters resistance and the eye is difficult, the drill is pulled out and the drilling tool assembly is replaced to clear the well.

3. The method for determining the cleanliness of a wellbore according to claim 1, characterized in that: The specific process of one cycle of K>2.5 is as follows: if the shape of the returned cuttings is normal, the short trip is verified, and the short trip can be successfully carried out, and the friction resistance is less than 5t, then drilling is resumed; if the returned cuttings are pieces of well wall peeling off, wellbore strengthening measures are taken to strengthen the well wall, the short trip is verified, and the short trip can be successfully carried out, and the friction resistance is less than 5t, then drilling is resumed.

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