A method for determining the oil-based mud content in crude oil samples extracted by a pump

Abstract

The invention discloses a method for determining the content of oil-based mud in a pump-extracted crude oil sample, which belongs to the technical field of oil and gas exploration, and includes: S1: obtaining formation crude oil in an oil and gas field and an oil-based mud sample for exploitation; S2: configuring mixed samples of oil-based mud and formation crude oil in multiple volume ratios; S3: obtaining the content data of straight-chain alkanes in each mixed sample; S4: constructing an oil-based mud content response factor Yz; S5: establishing a univariate linear regression model between the oil-based mud content response factor Yz and the volume ratio of oil-based mud to formation crude oil; S6: obtaining a univariate linear regression relationship between the oil-based mud content response factor Yz and the volume ratio of oil-based mud to formation crude oil; S7: obtaining the percentage of the content of oil-based mud in a pump-extracted crude oil sample in the same oil and gas field; S8: outputting the result. Compared with the existing chemical analysis method for obtaining the content of pump-extracted sampled oil-based mud, the whole process of the invention is simple, efficient and low-cost.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration, and in particular to a method for determining the content of oil-based mud in a crude oil sample extracted by a pump. Background Art

[0002] In order to improve the drilling efficiency of offshore oil and gas wells, the current drilling process mostly uses oil-based mud as the drilling fluid to protect the reservoir and increase the drilling speed. Since cable formation sampling is generally carried out in the completion stage, the oil and gas layer is often affected by the invasion of oil-based mud, that is, the pores around the wellbore wall of the drilling wellbore are filled with a mixture of oil-based mud and formation crude oil, resulting in cable formation sampling generally not being able to directly obtain pure formation crude oil samples. The samples generally contain oil-based mud, and the oil-based mud and formation crude oil are miscible, making it difficult to accurately separate formation crude oil and oil-based mud from the pumped samples. Cable formation sampling is the most direct means to prove the discovery of wellbore oil and gas. Therefore, in the process of pumping and sampling the target layer through the cable formation sampling instrument in offshore oil and gas wells, oilfield technicians are required to accurately evaluate the oil-based mud content in the pumped sample, in order to accurately determine the reservoir reserve parameters and formulate the optimal oilfield development implementation plan to achieve the purpose of increasing oilfield reserves and production.

[0003] Currently, determining the oil-based mud content in pumped samples mainly relies on a complicated laboratory analysis process: by using chemical analysis methods, such as gas chromatography-mass spectrometry (GC-MS), infrared spectroscopy, etc., to study the chemical composition of the pumped samples, first identify the crude oil and oil-based mud components in the sample, calculate the oil-based mud content of the pumped samples, and then deduct the oil-based mud content to calculate the content of formation crude oil in the pumped samples. Summary of the invention

[0004] The object of the present invention is to provide a method for determining the oil-based mud content in a crude oil sample extracted by a pump, so as to solve the problem that the process of determining the oil-based mud content by chemical analysis method is complicated.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] A method for determining the oil-based mud content in a crude oil sample extracted by a pump comprises the following steps:

[0007] S1: Obtaining crude oil from oil and gas fields and oil-based mud samples for development;

[0008] S2: mixed samples of oil-base mud and formation crude oil with various volume ratios of oil-base mud to formation crude oil;

[0009] S3: measuring each mixed sample to obtain the content data of straight-chain alkanes in each mixed sample: nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33;

[0010] S4: constructing the oil-based mud content response factor Yz through the content data of nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33 of each mixed sample;

[0011] S5: A univariate linear regression model between the oil-base mud content response factor Yz and the volume ratio of oil-base mud to formation crude oil is established using the least squares method;

[0012] S6: fitting analysis to obtain a univariate linear regression relationship between the oil-base mud content response factor Yz and the volume ratio of the oil-base mud to the formation crude oil;

[0013] S7: Obtain the percentage of oil-based mud in the crude oil sample extracted from the same oil and gas field according to a univariate linear regression relationship;

[0014] S8: Result output.

[0015] Furthermore, in the above step S2, the mixed samples include at least 5 types, and include at least three volume ratios of oil-based mud to formation crude oil, namely, 0%, 50%, and 100%.

[0016] Furthermore, there are 11 kinds of mixed samples, and the volume ratios of oil-based mud to formation crude oil are 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%, respectively.

[0017] Furthermore, in the above step S4, the expression of the oil-based mud content response factor Yz is: Yz=(nC13+nC14+nC15) / (nC13+nC14+nC15+nC21+nC25+nC30+nC31+nC32+nC33).

[0018] Furthermore, in the above step S6, during fitting, the correlation coefficient R of the univariate linear regression model is made not less than 0.99;

[0019] The linear regression relationship between the oil-based mud content response factor Yz and the volume ratio of oil-based mud to formation crude oil is:

[0020] Voil = a*Yz-b;

[0021] Wherein, Voil is the volume ratio of oil-based mud to formation crude oil; a and b are constants.

[0022] Furthermore, the above step S7 includes the following sub-steps:

[0023] S71: Obtain a pumped crude oil sample from the same oil and gas field;

[0024] S72: measuring the crude oil sample extracted by the pump, and obtaining the content data of the straight-chain alkanes in the crude oil sample extracted by the pump: nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33;

[0025] S73: constructing the oil-based mud content response factor Yz of the crude oil sample extracted by the pump;

[0026] S74: According to the univariate linear regression relationship between the oil-base mud content response factor Yz and the volume ratio of oil-base mud to formation crude oil, the volume ratio of oil-base mud to formation crude oil in the pumped crude oil sample is obtained, thereby obtaining the content percentage of oil-base mud in the pumped crude oil sample.

[0027] The present invention has the following beneficial effects:

[0028] The present invention is based on formation crude oil samples and oil-based mud samples, configures mixed liquids of different volume ratios, then obtains the content data of straight-chain alkanes in the mixed samples that are correlated with the oil-based mud content, and constructs the oil-based mud content response factor Yz, and then obtains the univariate linear regression relationship between the oil-based mud content response factor Yz and the volume ratio of oil-based mud to formation crude oil. Through the relationship, the percentage of oil-based mud content in crude oil samples extracted by any pump in the same oil and gas field can be obtained. The whole process is simple, efficient and low-cost. At the same time, the oil field production unit does not need to collect additional geological basic data, does not incur data collection operation fees, and only needs to process and mine the existing gas chromatography analysis data to realize the gas-oil ratio calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic flow chart of a method for determining the oil-based mud content in a crude oil sample extracted by a pump according to Example 1 of the present invention;

[0030] Figure 2 Schematic diagram of a univariate linear regression model according to Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0031] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0032] Embodiment 1:

[0033] Please refer to Figure 1 This embodiment provides a method for determining the oil-based mud content in a crude oil sample extracted by a pump, comprising the following steps:

[0034] S1: Obtain crude oil samples from oil and gas field formations and oil-based mud samples from mining through sampling instruments;

[0035] S2: preparing mixed samples of oil-base mud and formation crude oil with various volume ratios of oil-base mud to formation crude oil, each of which has a volume of 100 ml; the mixed samples include at least 5, i.e., at least 5 volume ratios of oil-base mud to formation crude oil, wherein the volume ratios of oil-base mud to formation crude oil include at least 0%, 50%, and 100%;

[0036] S3: measuring each mixed sample to obtain the content data of straight-chain alkanes in each mixed sample that are correlated with the oil-based mud content: nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32, and nC33; in this embodiment, nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32, and nC33 also represent their respective content data;

[0037] S4: Construct the oil-based mud content response factor Yz through the content data of nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33 of each mixed sample:

[0038] Yz=(nC13+nC14+nC15) / (nC13+nC14+nC15+nC21+nC25+nC30+nC31+nC32+nC33);

[0039] S5: A univariate linear regression model between the oil-base mud content response factor Yz and the volume ratio of oil-base mud to formation crude oil is established using the least squares method;

[0040] S6: Fitting analysis is used to obtain the univariate linear regression relationship between the oil-based mud content response factor Yz and the volume ratio of oil-based mud to formation crude oil. During fitting, the correlation coefficient R of the univariate linear regression model is made not less than 0.99. The univariate linear regression relationship between the oil-based mud content response factor Yz and the volume ratio of oil-based mud to formation crude oil is obtained as follows:

[0041] Voil = a*Yz-b;

[0042] Wherein, Voil is the volume ratio of oil-based mud to formation crude oil; a and b are constants.

[0043] S7: Obtaining the percentage of oil-based mud in the crude oil sample extracted from the same oil and gas field according to a univariate linear regression relationship, specifically comprising the following sub-steps:

[0044] S71: Obtain a pumped crude oil sample from the same oil and gas field;

[0045] S72: measuring the crude oil sample extracted by the pump, and obtaining the content data of the straight-chain alkanes in the crude oil sample extracted by the pump: nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33;

[0046] S73: constructing the oil-based mud content response factor Yz of the crude oil sample extracted by the pump;

[0047] S74: according to the univariate linear regression relationship between the oil-base mud content response factor Yz and the volume ratio of the oil-base mud to the formation crude oil, the volume ratio of the oil-base mud to the formation crude oil in the pumped crude oil sample is obtained, thereby obtaining the content percentage of the oil-base mud in the pumped crude oil sample;

[0048] S8: Result output.

[0049] The present invention is based on formation crude oil samples and oil-based mud samples, configures mixed liquids with different volume ratios, then obtains content data of straight-chain alkanes in the mixed samples that are correlated with the oil-based mud content, and constructs an oil-based mud content response factor Yz, then obtains a univariate linear regression relationship between the oil-based mud content response factor Yz and the volume ratio of the oil-based mud to the formation crude oil, and through the relationship, the content percentage of the oil-based mud in the crude oil sample extracted by any pump in the same oil and gas field can be obtained, and the whole process is simple, efficient and low-cost.

[0050] Embodiment 2:

[0051] This embodiment provides a specific example to illustrate the entire oil-based mud content determination method, which is not intended to limit the protection scope of the present invention.

[0052] This embodiment provides a method for calibrating the gas-oil ratio of a sample drawn by an oil-based mud pump, comprising the following steps:

[0053] S1: Obtain crude oil samples from oil and gas field formations and oil-based mud samples from mining through sampling instruments;

[0054] S2: preparing 10 mixed samples of oil-base mud and formation crude oil with different volume ratios of oil-base mud to formation crude oil, the volume of each mixed sample is 100 ml, and the volume ratios of oil-base mud to formation crude oil are: 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% respectively;

[0055] S3: Measure each mixed sample to obtain the content data of straight-chain alkanes in each mixed sample that are correlated with the oil-based mud content: nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33, as shown in Table 1; in this embodiment, nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33 also represent their respective content data;

[0056] Table 1 Straight-chain alkane content data of different oil-base mud and formation crude oil volume ratios

[0057]

[0058] S4: Construct the oil-based mud content response factor Yz through the content data of nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33 of each mixed sample:

[0059] Yz=(nC13+nC14+nC15) / (nC13+nC14+nC15+nC21+nC25+nC30+nC31+nC32+nC33);

[0060] The specific values ​​of the oil-based mud content response factor Yz corresponding to the volume ratio of each oil-based mud to formation crude oil are shown in Table 1;

[0061] S5: A univariate linear regression model between the oil-base mud content response factor Yz and the volume ratio of oil-base mud to formation crude oil is established using the least squares method;

[0062] S6: Fitting analysis obtains the univariate linear regression relationship between the oil-based mud content response factor Yz and the volume ratio of oil-based mud to formation crude oil. During fitting, the correlation coefficient R of the univariate linear regression model is 2 is 0.9975, and the obtained linear regression relationship between the oil-based mud content response factor Yz and the volume ratio of oil-based mud to formation crude oil is:

[0063] Voil = 1.5404 * Yz - 0.5496;

[0064] Wherein, Voil is the volume ratio of oil-based mud to formation crude oil.

[0065] S7: Obtaining the percentage of oil-based mud in the crude oil sample extracted from the same oil and gas field according to a univariate linear regression relationship, specifically comprising the following sub-steps:

[0066] S71: Obtain a pumped crude oil sample from the same oil and gas field;

[0067] S72: measuring the crude oil sample extracted by the pump, and obtaining the content data of the straight-chain alkanes in the crude oil sample extracted by the pump: nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33;

[0068] S73: constructing the oil-based mud content response factor Yz of the crude oil sample extracted by the pump;

[0069] S74: Substitute the oil-based mud content response factor Yz into the formula: Voil=1.5404*Yz-0.5496 to obtain the volume ratio of the oil-based mud to the formation crude oil in the pumped crude oil sample, thereby obtaining the content percentage of the oil-based mud in the pumped crude oil sample;

[0070] S8: Result output.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining the oil-based mud content in a crude oil sample extracted by a pump, characterized in that: The following steps are involved: S1: Obtaining crude oil from oil and gas fields and oil-based mud samples for development; S2: mixed samples of oil-base mud and formation crude oil with various volume ratios of oil-base mud to formation crude oil; S3: measuring each mixed sample to obtain the content data of straight-chain alkanes in each mixed sample: nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33; S4: constructing the oil-based mud content response factor Yz through the content data of nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33 of each mixed sample; S5: A univariate linear regression model between the oil-base mud content response factor Yz and the volume ratio of oil-base mud to formation crude oil is established using the least squares method; S6: fitting analysis to obtain a univariate linear regression relationship between the oil-base mud content response factor Yz and the volume ratio of the oil-base mud to the formation crude oil; S7: Obtain the percentage of oil-based mud in the crude oil sample extracted from the same oil and gas field according to a univariate linear regression relationship; S8: Result output.

2. The method for determining the oil-based mud content in a crude oil sample extracted by a pump according to claim 1, characterized in that: In step S2, the mixed samples include at least 5 types, and at least include three volume ratios of oil-based mud to formation crude oil, namely, 0%, 50%, and 100%.

3. The method for determining the oil-based mud content in a crude oil sample extracted by a pump according to claim 2, characterized in that: There are 11 kinds of mixed samples, and the volume ratios of oil-based mud to formation crude oil are 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%, respectively.

4. The method for determining the oil-based mud content in a crude oil sample extracted by a pump according to claim 1, characterized in that: In step S4, the expression of the oil-based mud content response factor Yz is: Yz=(nC13+nC14+nC15) / (nC13+nC14+nC15+nC21+nC25+nC30+nC31+nC32+nC33).

5. The method for determining the oil-based mud content in a crude oil sample extracted by a pump according to claim 1, characterized in that: In step S6, during fitting, the correlation coefficient R of the univariate linear regression model is made not less than 0.99; The linear regression relationship between the oil-based mud content response factor Yz and the volume ratio of oil-based mud to formation crude oil is: Voil = a*Yz-b; Wherein, Voil is the volume ratio of oil-based mud to formation crude oil; a and b are constants.

6. The method for determining the oil-based mud content in a crude oil sample extracted by a pump according to claim 5, characterized in that: Step S7 includes the following sub-steps: S71: Obtain a pumped crude oil sample from the same oil and gas field; S72: measuring the crude oil sample extracted by the pump, and obtaining the content data of the straight-chain alkanes in the crude oil sample extracted by the pump: nC13, nC14, nC15, nC21, nC25, nC30, nC31, nC32 and nC33; S73: constructing the oil-based mud content response factor Yz of the crude oil sample extracted by the pump; S74: According to the univariate linear regression relationship between the oil-base mud content response factor Yz and the volume ratio of oil-base mud to formation crude oil, the volume ratio of oil-base mud to formation crude oil in the pumped crude oil sample is obtained, thereby obtaining the content percentage of oil-base mud in the pumped crude oil sample.

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