Downhole condition judgment method based on drilling fluid performance change

Abstract

The invention relates to the technical field of oil-gas exploration, and relates to a drilling fluid performance change-based underground condition judgment method, which comprises the following steps of: stabilizing an ion environment of drilling fluid; setting safety values of density, apparent viscosity, temperature and conductivity of the drilling fluid based on the stratum environment of the drilling position; detecting the density, apparent viscosity, temperature and conductivity of the drilling fluid; wherein if the deviation between the detection values of the density, the apparent viscosity and the temperature of the drilling fluid and the corresponding safety value exceeds 5%, the output is abnormal, and if the deviation between the detection value of the conductivity and the corresponding safety value exceeds 20%, the output is abnormal; the abnormal conditions of the density, the apparent viscosity, the temperature and the conductivity of the drilling fluid are integrated, and abnormal judgment is output; and executing corresponding safety operation according to the output abnormal judgment type. According to the method, the abnormal conditions of all the performance parameters of the drilling fluid are integrated and then judged, the obtained underground conditions are more accurate and reliable, and the safety of oil-gas exploration is greatly improved.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas exploration, and in particular to a method for determining downhole conditions based on changes in drilling fluid properties. Background Art

[0002] In the process of oil and gas exploration and development, drilling operations are a key step in obtaining underground oil and gas resources. As an important medium in the drilling process, drilling fluid not only carries cuttings, cools and lubricates the drill bit, but also stabilizes the well wall and controls the formation pressure, which is crucial to the smooth progress of the drilling process. The properties of drilling fluid, including density, viscosity, water loss, solid content and ion content, directly affect the stability of drilling fluid and the safety of drilling operations.

[0003] However, the stability of drilling fluid performance is affected by many factors, such as formation water chemical properties, temperature, pressure, etc. The traditional use of drilling fluid performance to judge downhole conditions often focuses on a single performance parameter. This method is difficult to accurately reflect the changes in the downhole environment, resulting in an inability to make a more accurate judgment of the downhole situation. There is a situation where the judgment is significantly different from the actual situation downhole. Therefore, when the downhole environment is abnormal, correct safety operations cannot be made in a timely manner.

[0004] In view of this, there is an urgent need to provide a new method for judging the downhole situation, which can more accurately judge the downhole situation to ensure the safety of the oil and gas exploration process. Summary of the invention

[0005] The present application provides a method for determining downhole conditions based on changes in drilling fluid properties. Through multi-faceted evaluation, the downhole conditions can be determined more accurately and correct protective measures can be taken in a timely manner, thereby greatly improving the safety of oil and gas exploration.

[0006] The present application provides a method for determining downhole conditions based on changes in drilling fluid properties using the following technical solutions:

[0007] A method for determining downhole conditions based on changes in drilling fluid properties comprises the following steps:

[0008] Stabilize the ionic environment of the drilling fluid;

[0009] Based on the formation environment at the drilling location, set safe values ​​for the density, apparent viscosity, temperature and conductivity of the drilling fluid;

[0010] Detect the density, apparent viscosity, temperature and conductivity of drilling fluid;

[0011] Among them, if the detection value of the density, apparent viscosity and temperature of the drilling fluid deviates from the corresponding safety value by more than 5%, the output is abnormal; if the detection value of the conductivity deviates from the corresponding safety value by more than 20%, the output is abnormal;

[0012] Integrate the abnormal conditions of drilling fluid density, apparent viscosity, temperature and conductivity, and output abnormality judgment;

[0013] The abnormality determination includes solid phase invasion determination, oil invasion determination, abnormal high temperature determination of formation, metal ore drilling determination and drilling tool abrasion determination;

[0014] According to the type of abnormality determined by the output, the corresponding safety operation is performed.

[0015] Furthermore, if the detected value of the density of the drilling fluid is at least 5% higher than the corresponding safety value, and the detected value of the apparent viscosity is at least 5% higher than the corresponding safety value, the abnormal judgment output is a solid phase invasion judgment, and the safety operation setting is: starting the solid control device to remove harmful solid phases.

[0016] Further, detecting performance parameters of the drilling equipment, wherein the performance parameters of the drilling equipment include drilling tool weight on bit and drilling tool torque;

[0017] If the drilling pressure and the drilling torque of the drilling tool increase at the same time, the safety operation also includes: speed-controlled drilling and reserve plugging materials.

[0018] Furthermore, if the detected value of the density of the drilling fluid is at least 5% lower than the corresponding safety value, the detected value of the temperature is at least 5% lower than the corresponding safety value, and the detected value of the conductivity is at least 20% lower than the corresponding safety value, the abnormal judgment output is an oil invasion judgment, and the safety operation setting is: shutting in the well or killing the well.

[0019] Further, detecting performance parameters of the drilling equipment, wherein the performance parameters of the drilling equipment include drilling tool weight on bit and drilling tool torque;

[0020] If the drilling pressure of the drill tool decreases, the torque of the drill tool fluctuates greatly, and the drilling fluid is accompanied by bubbles and a foul smell, the safety operation setting is: shutting down the well, preparing alkaline weighted drilling fluid and mixing it with the initial drilling fluid.

[0021] Furthermore, if the detected value of the temperature of the drilling fluid is at least 5% higher than the corresponding safety value, and the detected value of the conductivity is at least 20% higher than the corresponding safety value, the abnormal judgment output is a drill tool abrasion judgment, and the safety operation is set to: stop drilling, observe and replace the abrasive drill tools after pulling out the drill.

[0022] Further, if the detected value of the density of the drilling fluid is at least 5% higher than the corresponding safety value, the detected value of the temperature is at least 5% higher than the corresponding safety value, and the detected value of the conductivity is at least 20% higher than the corresponding safety value, the abnormality determination output is a determination of metal mineral deposit drilling;

[0023] The safety operation setting is: continue drilling, start the solid control device to remove harmful solid phase, and make the deviation between the detection value of the drilling fluid density and the safety value less than 5%.

[0024] Furthermore, if the detected value of the temperature of the drilling fluid is at least 5% higher than the corresponding safety value, and the detected value of the apparent viscosity is at least 5% higher than the corresponding safety value, the abnormal judgment output is an abnormally high temperature judgment of the formation, and the safety operation setting is: speed controlled drilling, and adding high temperature resistant drilling fluid treatment agent to the drilling fluid.

[0025] Furthermore, the step of stabilizing the ionic environment of the drilling fluid comprises the following steps:

[0026] Based on the formation environment at the drilling location, set safe values ​​for chloride ions, calcium ions, sulfur ions and pH values;

[0027] Detect the concentration of chloride ions, calcium ions, sulfur ions and the pH value of drilling fluid;

[0028] If any of the detected values ​​of chloride ion, calcium ion, sulphur ion or pH value deviates from the corresponding safety value by more than 5%, add adjustment medium into the well;

[0029] If the deviation between any of the detected values ​​of chloride ion, calcium ion, sulfur ion or pH value and the corresponding safety value is less than 5%, proceed to the next step.

[0030] Furthermore, the adjustment medium includes NaCl, CaCl2, CaSO4, NaOH, Ca(OH)2, and CaCO3.

[0031] In summary, the present application includes at least one of the following beneficial technical effects:

[0032] 1. The judgment method in this application can timely discover abnormal conditions downhole by real-time monitoring of changes in drilling fluid performance, and report them in time to assist in analysis and confirmation of fluid intrusion, so as to take corresponding measures to avoid accidents and ensure the safety of drilling operations.

[0033] 2. The judgment method in this application refers to multiple drilling fluid performance parameters at the same time. When one of the performance parameters is abnormal, there may be situation 1, situation 2 or situation 3. By integrating the abnormal states of multiple drilling fluid performance parameters, common situations are found and finally an abnormal judgment is output. Compared with the method of considering a single drilling fluid performance parameter, it can more accurately reflect the changes in the downhole environment and make oil and gas exploration safer and more efficient.

[0034] 3. The judgment method in this application uses the change in the performance parameters of the drilling fluid as the main reference when outputting abnormal judgments. On this basis, it will further refer to the performance parameters of the drilling equipment to verify the accuracy of the output abnormal judgments. At the same time, in the corresponding abnormal judgment situations, it analyzes more specific downhole conditions and takes more appropriate safety operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of the downhole judgment method in this application. DETAILED DESCRIPTION

[0036] The following will be combined with the attached Figure 1 The technical solution of the present application is described clearly and completely. The following embodiments are exemplary and are only used to explain the present application, and cannot be interpreted as limiting the present application. In the following description, the same symbols are used to represent the same or equivalent elements, and repeated descriptions are omitted.

[0037] In the description of the present application, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present application are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0038] In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0039] It should be further understood that the term “and / or” used in the specification and corresponding claims of this application refers to any and all possible combinations of one or more of the listed items.

[0040] A method for judging downhole conditions based on changes in drilling fluid properties, referring to Figure 1 , including the following steps:

[0041] S1. Stabilize the ionic environment of the drilling fluid;

[0042] Specifically, stabilizing the ionic environment of the drilling fluid includes the following steps:

[0043] S11. Based on the formation environment at the drilling location, set the safety values ​​of chloride ions, calcium ions, sulfur ions and pH value;

[0044] S12, detecting the concentration of chloride ions, calcium ions, and sulfur ions in the drilling fluid and the pH value of the drilling fluid;

[0045] If any of the detected values ​​of chloride ion, calcium ion, sulphur ion or pH value deviates from the corresponding safety value by more than 5%, add adjustment medium into the well;

[0046] If the deviation between any of the detected values ​​of chloride ion, calcium ion, sulfur ion or pH value and the corresponding safety value is less than 5%, proceed to the next step.

[0047] Among them, the detection of chloride ions, calcium ions and sulfur ions is to ensure that there is no water in the formation. Under normal circumstances, if water comes out of the formation, the detection values ​​of chloride ions, calcium ions and sulfur ions will be at least 5% lower than the safety value. The pH value is tested to ensure that there is no acidic gas. If there is acidic gas in the well, the pH value will be at least 5% lower than the safety value.

[0048] Correspondingly, the adjusting medium includes NaCl, CaCl2, CaSO4, NaOH, Ca(OH)2, and CaCO3.

[0049] When any abnormal content of chloride ion, calcium ion and sulfur ion is detected, salt substances such as NaCl, CaCl2, CaSO4 will be added to the drilling fluid to form a weighted drilling fluid. When an abnormal pH value is detected, alkaline substances such as NaOH, Ca(OH)2, CaCO3 will be added to the drilling fluid to form an alkaline drilling fluid. When an abnormal pH value is detected, any abnormal content of chloride ion, calcium ion and sulfur ion is also detected, and salt substances and alkaline sites are added to the drilling fluid to form an alkaline weighted drilling fluid.

[0050] By adding adjusting media to the drilling fluid, we can cope with the occurrence of water and acid gas in the underground formation and ensure that drilling continues in a stable manner.

[0051] In addition, if the detection values ​​of chloride ions, calcium ions and sulfur ions will be at least 5% lower than the safety value after the adjustment medium is added, the well should be shut down in time.

[0052] It should be noted that the safety values ​​of chloride ions, calcium ions, sulfur ions and pH values ​​are determined based on the geological environment of the drilling location. When conducting oil and gas exploration in different regions, the safety values ​​obtained from field surveys will vary.

[0053] S2. Based on the formation environment at the drilling location, set safe values ​​for the density, apparent viscosity, temperature and conductivity of the drilling fluid;

[0054] S3. Detect the density, apparent viscosity, temperature and conductivity of the drilling fluid;

[0055] Among them, if the detection value of the density, apparent viscosity and temperature of the drilling fluid deviates from the corresponding safety value by more than 5%, the output is abnormal; if the detection value of the conductivity deviates from the corresponding safety value by more than 20%, the output is abnormal;

[0056] S4, integrating the abnormal conditions of the density, apparent viscosity, temperature and conductivity of the drilling fluid, and outputting the abnormality judgment;

[0057] Among them, abnormality determination includes solid phase invasion determination, oil invasion determination, abnormal high temperature determination of formation, metal mineral deposit drilling determination and drilling tool abrasion determination;

[0058] S5. Execute corresponding safety operations according to the type of abnormality output.

[0059] Furthermore, if the detected value of the density of the drilling fluid is at least 5% higher than the corresponding safety value, and the detected value of the apparent viscosity is at least 5% higher than the corresponding safety value, the abnormal judgment output is a solid phase invasion judgment, and the safety operation is set to: start the solid control device to remove harmful solid phases.

[0060] In addition, under the premise of taking the change of the performance parameters of the drilling fluid as the main reference, the performance parameters of the drilling equipment are further referred to. Correspondingly, the judgment method also includes: detecting the performance parameters of the drilling equipment, and the performance parameters of the drilling equipment include the drilling pressure and the drilling torque of the drill bit.

[0061] Taking the case where the abnormal judgment output is solid phase invasion judgment as an example, if the drilling pressure and drilling torque of the drill bit increase at the same time, it indicates that a relatively hard formation may be encountered during the drilling process, and there may be complex geological structures in the formation. At this time, it can be more certain that solid phase invasion occurs underground during the drilling process.

[0062] At the same time, in this case, in addition to starting the solid control device to remove harmful solid phases, safe operations also include: controlling the drilling speed, confirming the formation encountered, and reserving plugging materials to reduce the possibility of leakage after drilling into igneous rocks.

[0063] Furthermore, if the detected value of the density of the drilling fluid is at least 5% lower than the corresponding safety value, the detected value of the temperature is at least 5% lower than the corresponding safety value, and the detected value of the conductivity is at least 20% lower than the corresponding safety value, the abnormal judgment output is oil invasion judgment, and the safety operation is set to: shut in the well or kill the well.

[0064] Among them, shut-in or well killing is specifically set according to the actual situation. When oil invasion occurs in the well, well killing operation is usually carried out, that is, the drilling fluid is increased in weight. If the density of the drilling fluid decreases too much, for example, if the detected value of the density of the drilling fluid is about 20% lower than the corresponding safety value, the well shut-in operation is performed.

[0065] In addition, further reference can be made to other performance parameters of the drilling fluid and the performance parameters of the drilling equipment for further comprehensive consideration to analyze and obtain a more detailed downhole situation.

[0066] Specifically, in a specific embodiment, if the drilling pressure of the drill bit decreases, the drilling torque fluctuates greatly (10% above and below the normal range), and the drilling fluid is accompanied by bubbles and a foul odor, the safety operation setting is: shutting down the well and preparing alkaline weighted drilling fluid to mix with the initial drilling fluid.

[0067] That is, when determining the downhole situation, the drilling fluid density, apparent viscosity, temperature and conductivity are used as the main benchmarks, and the abnormal conditions of these four performance parameters are integrated to make abnormal determinations. Other performance parameters of the drilling fluid (such as the above-mentioned gas measurement value, odor, etc.) and the performance parameters of the drilling equipment are also further considered during the determination. Further analysis can be performed to obtain more specific downhole conditions, and the safe operation under the corresponding abnormal determination can be adjusted, thereby improving safety.

[0068] The following is a specific application example of Well 1 in the Ledong Depression of the Qiongdongnan Basin in the western waters of the South China Sea of ​​CNOOC as an example of the present embodiment. The well is a high-temperature and high-pressure well, and the drilling fluid used is a water-based drilling fluid. When drilling to 4431m, it was detected that the density and conductivity of the drilling fluid both dropped to an abnormal state. At the same time, the density and rheological curves of the drilling fluid both showed obvious fluctuations. The density of the drilling fluid dropped from 1.93g / cm3 to 1.89g / cm3, the apparent viscosity (AV) dropped from 34mPa·s to 32mPa·s, the plastic viscosity (PV) dropped from 29mPa·s to 26mPa·s, and the funnel viscosity (FV) dropped from 44s to 43s.

[0069] Based on this, the abnormality determination output is oil intrusion determination.

[0070] Furthermore, other performance parameters of the drilling fluid were tested and it was found that the gas measurement value increased from 0.3% to 11%, which further suggested the possibility that the formation near 4431m contained a small amount of bottom water while mixing with gas.

[0071] Furthermore, if the detected value of the temperature of the drilling fluid is at least 5% higher than the corresponding safety value, and the detected value of the conductivity is at least 20% higher than the corresponding safety value, the abnormal judgment output is a drill tool abrasion judgment, and the safety operation is set as: stop drilling, observe and replace the abrasive drill tools after pulling out the drill.

[0072] Furthermore, if the detected value of the density of the drilling fluid is at least 5% higher than the corresponding safety value, the detected value of the temperature is at least 5% higher than the corresponding safety value, and the detected value of the conductivity is at least 20% higher than the corresponding safety value, the abnormal judgment output is a metal mineral drilling judgment; the safety operation setting is: continue drilling, start the solid control device to remove harmful solid phases, so that the deviation between the detected value of the density of the drilling fluid and the safety value is less than 5%.

[0073] Furthermore, if the detected value of the temperature of the drilling fluid is at least 5% higher than the corresponding safety value, and the detected value of the apparent viscosity is at least 5% higher than the corresponding safety value, the abnormal judgment output is an abnormally high temperature judgment of the formation, and the safety operation setting is: speed controlled drilling, adding high temperature resistant drilling fluid treatment agent to the drilling fluid to replace the ordinary drilling fluid treatment agent originally added to the drilling fluid.

[0074] The embodiments of this specific implementation are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. The same components are represented by the same figure marks. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for determining downhole conditions based on changes in drilling fluid properties, characterized in that: The following steps are involved: Stabilize the ionic environment of the drilling fluid; Based on the formation environment at the drilling location, set safe values ​​for the density, apparent viscosity, temperature and conductivity of the drilling fluid; Detect the density, apparent viscosity, temperature and conductivity of drilling fluid; Among them, if the detection value of the density, apparent viscosity and temperature of the drilling fluid deviates from the corresponding safety value by more than 5%, the output is abnormal; if the detection value of the conductivity deviates from the corresponding safety value by more than 20%, the output is abnormal; Integrate the abnormal conditions of drilling fluid density, apparent viscosity, temperature and conductivity, and output abnormality judgment; The abnormality determination includes solid phase invasion determination, oil invasion determination, abnormal high temperature determination of formation, metal ore drilling determination and drilling tool abrasion determination; According to the type of abnormality determined by the output, the corresponding safety operation is performed.

2. The determination method according to claim 1, characterized in that: If the detected value of the density of the drilling fluid is at least 5% higher than the corresponding safety value, and the detected value of the apparent viscosity is at least 5% higher than the corresponding safety value, the abnormal judgment output is a solid phase invasion judgment, and the safety operation setting is: starting the solid control device to remove harmful solid phases.

3. The determination method according to claim 2, characterized in that: Detecting performance parameters of the drilling equipment, wherein the performance parameters of the drilling equipment include drilling pressure and drilling torque of the drilling tool; If the drilling pressure and the drilling torque of the drilling tool increase at the same time, the safety operation also includes: speed-controlled drilling and reserve plugging materials.

4. The determination method according to claim 1, characterized in that: If the detected value of the density of the drilling fluid is at least 5% lower than the corresponding safety value, the detected value of the temperature is at least 5% lower than the corresponding safety value, and the detected value of the conductivity is at least 20% lower than the corresponding safety value, the abnormal judgment output is an oil invasion judgment, and the safety operation setting is: shutting in the well or killing the well.

5. The determination method according to claim 4, characterized in that: Detecting performance parameters of the drilling equipment, wherein the performance parameters of the drilling equipment include drilling pressure and drilling torque of the drilling tool; If the drilling pressure of the drill tool decreases, the torque of the drill tool fluctuates greatly, and the drilling fluid is accompanied by bubbles and a foul smell, the safety operation setting is: shutting down the well, preparing alkaline weighted drilling fluid and mixing it with the initial drilling fluid.

6. The determination method according to claim 1, characterized in that: If the detected value of the temperature of the drilling fluid is at least 5% higher than the corresponding safety value, and the detected value of the conductivity is at least 20% higher than the corresponding safety value, the abnormal judgment output is a drill tool abrasion judgment, and the safety operation setting is: stop drilling, observe and replace the abrasive drill tools after pulling out the drill.

7. The determination method according to claim 1, characterized in that: If the detected value of the density of the drilling fluid is at least 5% higher than the corresponding safety value, the detected value of the temperature is at least 5% higher than the corresponding safety value, and the detected value of the conductivity is at least 20% higher than the corresponding safety value, the abnormality determination output is a determination of metal mineral deposit drilling; The safety operation setting is: continue drilling, start the solid control device to remove harmful solid phase, and make the deviation between the detection value of the drilling fluid density and the safety value less than 5%.

8. The determination method according to claim 1, characterized in that: If the detected value of the temperature of the drilling fluid is at least 5% higher than the corresponding safety value, and the detected value of the apparent viscosity is at least 5% higher than the corresponding safety value, the abnormal judgment output is an abnormally high temperature judgment of the formation, and the safety operation setting is: speed controlled drilling, adding high temperature resistant drilling fluid treatment agent to the drilling fluid.

9. The determination method according to claim 1, characterized in that: The step of stabilizing the ionic environment of the drilling fluid comprises the following steps: Based on the formation environment at the drilling location, set safe values ​​for chloride ions, calcium ions, sulfur ions and pH values; Detect the concentration of chloride ions, calcium ions, sulfur ions and the pH value of drilling fluid; If any of the detected values ​​of chloride ion, calcium ion, sulphur ion or pH value deviates from the corresponding safety value by more than 5%, add adjustment medium into the well; If the deviation between any of the detected values ​​of chloride ion, calcium ion, sulfur ion or pH value and the corresponding safety value is less than 5%, proceed to the next step.

10. A method for determining downhole conditions of performance changes in a drilling fluid ion stable environment according to claim 9, characterized in that: The adjusting medium includes NaCl, CaCl2, CaSO4, NaOH, Ca(OH)2, and CaCO3.

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