Characterization method for controlling enrichment of organic matters in hydrocarbon source rock by tuff

Abstract

The invention relates to the technical field of oil and gas geological exploration, in particular to a characterization method for controlling enrichment of hydrocarbon source rock organic matters by tuff, which comprises the following steps: selecting an interbed development area of a tuff layer and a shale layer, and continuously sampling the shale layer covering the tuff layer; taking organic matter abundance TOC as an evaluation index of the organic matter abundance; the distance between the tuff layer and the overlying rock sample is used as an evaluation index of the organic matter enrichment control intensity; taking P / Al, Cu / Al and Ni / Al as evaluation indexes of the organic matter production capacity; taking the molybdenum enrichment coefficient and the ratio of the molybdenum enrichment coefficient to the uranium enrichment coefficient as evaluation indexes of oxidation-reduction conditions of the sedimentary environment to obtain an organic matter enrichment degree classification interval; and taking the sum of the standardized evaluation indexes as an organic matter enrichment degree judgment index, and further constructing an organic matter enrichment degree range interval for judging the organic matter enrichment degree. The method has important indicating significance on shale oil dessert area prediction.

Description

Technical Field

[0001] This invention relates to the field of oil and gas geological exploration technology, specifically to a characterization method for the enrichment control of organic matter in source rocks by tuff. Background Technology

[0002] Paleovolcanic activity significantly influenced the organic matter production capacity and redox conditions of lacustrine sedimentary waters. Existing methods primarily focused on qualitative descriptions of the impact of volcanic activity, lacking quantitative parameter characterization studies. Furthermore, modern volcanic activity research mainly concentrates on the deposition of single volcanic events, and related technologies cannot match the impact of millions of years of volcanic activity in paleostratigraphic periods. Therefore, research on the sedimentary environment of surrounding source rocks caused by paleovolcanic activity still needs to be conducted using paleostratigraphic data. There is a significant positive correlation between the enrichment of major and trace elements such as P, Cu, and Ni in lacustrine sediments and the enrichment of organic matter. P is a nutrient element required for organic matter generation, while Cu and Ni are mainly enriched in organic matter sediments through their combination and adsorption. Therefore, the contents of P, Cu, and Ni indicate the paleoproductivity of organic matter. Thus, the relative levels of organic matter production capacity can be calculated by utilizing the differences in these major and trace elements in paleostratigraphic sediments.

[0003] In addition, the redox conditions of lake basin sedimentary water have a significant impact on the species and quantity of organisms and the enrichment of organic matter. The higher the reducing power, the more favorable it is for the enrichment of organic matter. This can be inferred by analyzing and measuring the redox-sensitive elements (Mo, U) or their enrichment coefficients in sedimentary rocks.

[0004] This invention explores a method to quantitatively characterize the organic matter production capacity and redox conditions of volcanic tuff on the sedimentary water of overlying source rocks using parameters such as organic matter abundance (TOC) and major and trace element concentrations. It also establishes a graded evaluation standard to clarify the degree of control of ancient volcanic activity on the enrichment of organic matter in source rocks, which has important indicative significance for the prediction of shale oil sweet spots. Summary of the Invention

[0005] The present invention aims to address the above-mentioned problems by proposing a characterization method for the enrichment and control of organic matter in source rocks by tuff.

[0006] The technical solution of this invention is as follows: The characterization method for the control of organic matter enrichment in source rocks by tuff is as follows: In areas where tuff and shale layers are interbedded, rock samples are continuously taken from the shale layer overlying the tuff layer. The total organic matter abundance (TOC) was used as the evaluation index for organic matter abundance; the distance between the tuff layer and its overlying rock sample was used as the evaluation index for the strength of organic matter enrichment control; P / Al, Cu / Al, and Ni / Al were used as evaluation indexes for organic matter production capacity; and the molybdenum enrichment coefficient and the ratio of the molybdenum enrichment coefficient to the uranium enrichment coefficient were used as evaluation indexes for the redox conditions of the sedimentary environment. The fitting relationship between organic matter abundance (TOC) and other evaluation indicators was constructed to obtain the classification intervals of organic matter enrichment. The evaluation indicators of each organic matter enrichment classification interval were standardized, and the sum of the standardized evaluation indicators was used as the organic matter enrichment determination index. The organic matter enrichment range interval was constructed based on the organic matter enrichment determination index to determine the organic matter enrichment degree.

[0007] The range of organic matter abundance (TOC) is denoted as the organic matter abundance TOC interval, specifically TOC < 1, 1 ≤ TOC < 2, 2 ≤ TOC < 4, and TOC ≥ 4.

[0008] The specific process for obtaining the organic matter enrichment level classification interval is as follows: the fitting formula for the organic matter abundance TOC and each evaluation index is y=ae. bx x represents the actual measured value of TOC, %; y represents the values ​​of each evaluation index corresponding to x; a and b are both fitting coefficients; let x be... 端点 Let x be the values ​​of x when x = 1, 2, 4, %; x 端点 The corresponding y is denoted as y 端点 ; and then according to y 端点 The intervals of other evaluation indicators corresponding to the organic matter abundance TOC intervals were obtained; thus, 7 groups of organic matter enrichment range intervals, including the organic matter abundance TOC intervals, were obtained.

[0009] The specific process for obtaining the intervals of the remaining evaluation indicators is as follows: determine whether the organic matter abundance (TOC) is positively or negatively correlated with each evaluation indicator; if positively correlated, then x 端点 When y = 1, the corresponding y is the lower limit; otherwise, it is the upper limit; thus, the range of organic matter enrichment degree is obtained.

[0010] The specific process for obtaining the range of organic matter enrichment is as follows: Let the organic matter enrichment degree judgment index be Y. x端点 ';When x 端点 When the values ​​are 1, 2, and 4, three organic matter enrichment level indicators Y1', Y2', and Y4' are obtained respectively. When the target organic matter enrichment level Y < Y1', the organic matter enrichment level is level IV; when Y1' ≤ Y < Y2', the organic matter enrichment level is level III; when Y2' ≤ Y < Y4', the organic matter enrichment level is level II; and when Y ≥ Y4', the organic matter enrichment level is level I.

[0011] The organic matter enrichment degree determination index Y x端点 The specific solution process is as follows: Y x端点 '=∑y ix端点 ';i=1,2…7,x 端点 =1,2,4; In the formula: Y x端点 'These are indicators for determining the degree of organic matter enrichment, specifically including Y1', Y2', and Y4'. y ix端点 'Let ' be the i-th evaluation index in x respectively 端点 The standardized values ​​of y when =1, 2, 4.

[0012] The specific solution process for the target organic matter enrichment degree Y is as follows: Y=∑y ix '; In the formula: Y represents the enrichment degree of the target organic matter; y ix ' represents the standardized value of y corresponding to the i-th evaluation index and x.

[0013] The specific process of standardization is as follows: y ix端点 '=(y ix端点 -y imin ) / (y imax -y imin ) y ix '=(y ix -y imin ) / (y imax -y imin ) In the formula: y ix端点 For the i-th evaluation index, respectively in x 端点 The y values ​​corresponding to =1,2,4; y imin Let y be the value of the i-th evaluation index when x=0.1; y imax The y-value is the value of the i-th evaluation index when the maximum value of the actual measured value of x=TOC is rounded up. y ix Let y be the y-value corresponding to x for the i-th evaluation index.

[0014] The specific formulas for calculating the molybdenum enrichment coefficient and the uranium enrichment coefficient are as follows: Mo EF =(Mo 测量值 / Al 计算值 ) / (Mo PAAS / Al PAAS ); U EF =(U 测量值 / Al 计算值 ) / (U PAAS / Al PAAS ); In the formula: Mo 测量值 U 测量值 The values ​​are the measured contents of Mo and U elements in the rock sample, in grams; Al 计算值 The calculated content of Al in the rock sample is given in g; Mo... PAAS Al PAAS and U PAAS These are the average contents of Mo, Al, and U elements in Post-Archaeological Australian shale, in grams.

[0015] The technical effects of this invention are as follows: This invention explores a quantitative characterization of organic matter production capacity and redox conditions of sedimentary environment through the concentration of major and trace elements, and establishes a graded evaluation standard to clarify the degree of control of ancient volcanic activity on the enrichment of organic matter in source rocks, which has important indicative significance for the prediction of shale oil sweet spots. Attached Figure Description

[0016] Figure 1 This is a plate showing the correlation between total organic matter abundance (TOC) and the distance between the tuff layer and its overlying rock sample.

[0017] Figure 2 This is a graph showing the correlation between total organic matter (TOC) and the P / Al ratio.

[0018] Figure 3 This is a chart showing the correlation between organic matter abundance (TOC) and the Cu / Al ratio.

[0019] Figure 4 This is a chart showing the correlation between organic matter abundance (TOC) and Ni / Al.

[0020] Figure 5 For organic matter abundance TOC and Mo EF Related images and figures.

[0021] Figure 6 For organic matter abundance TOC and Mo EF / U EF Related images and figures. Detailed Implementation

[0022] A method for characterizing the control of tuff on the enrichment of organic matter in source rocks, the method is as follows: Step 1: Select an area where tuff and shale layers are interbedded, and continuously sample the shale layer overlying the tuff to obtain rock samples; Step 2: Construct the fitting relationship between organic matter abundance (TOC) and other evaluation indicators, y=ae bx The results showed a negative correlation between organic matter abundance (TOC) and the distance between the tuff layer and its overlying rock sample, and a negative correlation with P / Al, Cu / Al, Ni / Al, and Mo. EF and Mo EF / U EF All are positively correlated; Based on experience, the range of total organic matter abundance (TOC) is: TOC < 1, 1 ≤ TOC < 2, 2 ≤ TOC < 4, and TOC ≥ 4, with the endpoint value x being taken. 端点 =1, 2, and 4; substituting these values ​​into the fitting formula for the organic matter abundance (TOC) and the other evaluation indicators, we obtain x. 端点 y = 1, 2 and 4 端点 , which represents the endpoint values ​​of each evaluation index; since there is a negative correlation between organic matter abundance (TOC) and the distance between the tuff layer and its overlying rock sample, for the evaluation index of the distance between the tuff layer and its overlying rock sample, x 端点 =1 corresponds to an upper limit for the y-value; for the evaluation indicators P / Al, Cu / Al, Ni / Al, Mo EF and Mo EF / U EF x 端点 =1 corresponds to the lower limit of the y-value; therefore, the specific range of organic matter enrichment is shown in columns 1-7 of Table 1: Table 1. Range of Organic Matter Enrichment Degree and Criteria for Judging Organic Matter Enrichment Degree ; Among them, y i1 For x 端点 When y = 1, the y-value corresponding to the i-th evaluation index is... i2 For x 端点 When = 2, the y-value corresponding to the i-th evaluation index is y. i4 For x 端点 When =4, the y-value corresponding to the i-th evaluation index, where i takes the range of 1-7; Step 3: x 端点 When =1, y i1 Standardization yields y in sequence 11 '、y 21 '、y 31 '、y 41 '、y 51 '、y 61 'and y 71Summing the results yields Y1'; similarly, Y2' and Y4' are obtained; furthermore, when the target organic matter enrichment level Y < Y1', the organic matter enrichment level is level IV; when Y1' ≤ Y < Y2', the organic matter enrichment level is level III; when Y2' ≤ Y < Y4', the organic matter enrichment level is level II; and when Y ≥ Y4', the organic matter enrichment level is level I.

[0023] Specific experimental cases Step 1: Sampling; In an area where tuff and shale layers are interbedded, rock samples were continuously taken from the shale layer overlying the tuff layer. A total of 6 rock samples were taken, each with a diameter of 0.5 cm and a length of 0.5 cm to 1 cm. Step 2: Construct fitting equations between Total Organic Matter (TOC) and the other evaluation indicators, as detailed below. Figures 1 to 6 Take x 端点 y = 1, 2 and 4 端点 The specific solution process for the remaining evaluation indicators is as follows: P / Al=P 计算值 / Al 计算值 = (P molecular weight percentage × P2O) 5测量值 ×10 -2 ) / (Al molecular weight percentage × Al2O) 3测量值 ×10 -2 ); where, the molecular mass percentage of P = (2×31) ÷ (2×31+5×16) ≈ 0.4366; the molecular mass percentage of Al = (2×27) ÷ (2×27+3×16) ≈ 0.5496; Cu / Al=Cu 测量值 / Al 计算值 Ni / Al=Ni 测量值 / Al 计算值 ; Mo EF =(Mo 测量值 / Al 计算值 ) / (Mo PAAS / Al PAAS );U EF =(U 测量值 / Al 计算值 ) / (U PAAS / Al PAAS ); In the formula: P 计算值 The calculated content of phosphorus (P) in the rock sample is expressed in grams; Al 计算值 The calculated content of Al in the rock sample is expressed in g; P2O 5测量值 The measured values ​​of P2O5 content in the rock sample are %; Al2O 3测量值 The measured values ​​of Al2O3 content in the rock sample are %; Cu测量值 Ni 测量值 Mo 测量值 and U 测量值 The values ​​are the measured contents of Cu, Ni, Mo, and U elements in the rock sample, in grams; Mo PAAS Al PAAS and U PAAS These are the average contents of Mo, Al, and U elements in Post-Archaeological Australian shale, in grams; among them, Mo PAAS The value is 1.0 × 10. -6 g, Al PAAS Value 100000 × 10 -6 g, U PAAS The value is 3.1 × 10 -6 g; This constitutes the range of organic matter enrichment levels, as shown in columns 1-7 of Table 2. Step 3: x 端点 When =1, y i1 Standardization yields y in sequence 11 '、y 21 '、y 31 '、y 41 '、y 51 '、y 61 'and y 71 Summing the results yields Y1'; similarly, Y2' and Y4' are obtained; the range of organic matter enrichment is then defined as shown in column 8 of Table 2. If the target organic matter enrichment level Y < Y1', the organic matter enrichment level is level IV; if Y1' ≤ Y < Y2', the organic matter enrichment level is level III; if Y2' ≤ Y < Y4', the organic matter enrichment level is level II; and if Y ≥ Y4', the organic matter enrichment level is level I, thus achieving the characterization of the organic matter enrichment level. Table 2. Ranges of organic matter enrichment and criteria for judging organic matter enrichment in specific experimental cases. .

Claims

1. A method for characterizing the enrichment control of organic matter in source rocks by tuff, characterized in that, The method is as follows: In areas where tuff and shale layers are interbedded, rock samples are continuously taken from the shale layer overlying the tuff layer. The total organic matter abundance (TOC) was used as the evaluation index for organic matter abundance; the distance between the tuff layer and its overlying rock sample was used as the evaluation index for the strength of organic matter enrichment control; P / Al, Cu / Al, and Ni / Al were used as evaluation indexes for organic matter production capacity; and the molybdenum enrichment coefficient and the ratio of the molybdenum enrichment coefficient to the uranium enrichment coefficient were used as evaluation indexes for the redox conditions of the sedimentary environment. The fitting relationships between organic matter abundance (TOC) and other evaluation indicators were constructed to obtain the classification intervals of organic matter enrichment. The evaluation indicators for each organic matter enrichment level classification interval are standardized, and the sum of the standardized evaluation indicators is used as the organic matter enrichment level judgment index. The organic matter enrichment level range interval is constructed based on the organic matter enrichment level judgment index to determine the organic matter enrichment level.

2. The characterization method for the enrichment control of organic matter in source rocks by tuff according to claim 1, characterized in that, The range of organic matter abundance (TOC) is denoted as the organic matter abundance TOC interval, specifically TOC < 1, 1 ≤ TOC < 2, 2 ≤ TOC < 4, and TOC ≥ 4.

3. The characterization method for the control of organic matter enrichment in source rocks by tuff according to claim 2, characterized in that, The specific process for obtaining the organic matter enrichment level classification interval is as follows: the fitting formula for the organic matter abundance TOC and each evaluation index is y=ae. bx x represents the actual measured value of TOC, y represents the values ​​of each evaluation index corresponding to x, and a and b are both fitting coefficients; let x be... 端点 Let x be the values ​​of x when x = 1, 2, 4. 端点 The corresponding y is denoted as y 端点 ; and then according to y 端点 The intervals of other evaluation indicators corresponding to the organic matter abundance TOC intervals were obtained; thus, 7 groups of organic matter enrichment range intervals, including the organic matter abundance TOC intervals, were obtained.

4. The characterization method for the enrichment control of organic matter in source rocks by tuff according to claim 3, characterized in that, The specific process for obtaining the intervals of the remaining evaluation indicators is as follows: determine whether the organic matter abundance (TOC) is positively or negatively correlated with each evaluation indicator; if positively correlated, then x 端点 When y = 1, the corresponding y is the lower limit; otherwise, it is the upper limit; thus, the range of organic matter enrichment degree is obtained.

5. The characterization method for the enrichment control of source rock organic matter by tuff according to claim 4, characterized in that, The specific process for obtaining the range of organic matter enrichment is as follows: Let the organic matter enrichment degree judgment index be Y. x端点 ';When x 端点 When the values ​​are 1, 2, and 4, three organic matter enrichment level indicators Y1', Y2', and Y4' are obtained respectively. When the target organic matter enrichment level Y < Y1', the organic matter enrichment level is level IV; when Y1' ≤ Y < Y2', the organic matter enrichment level is level III; when Y2' ≤ Y < Y4', the organic matter enrichment level is level II; and when Y ≥ Y4', the organic matter enrichment level is level I.

6. The characterization method for the enrichment control of organic matter in source rocks by tuff according to claim 5, characterized in that, The organic matter enrichment degree determination index Y x端点 The specific solution process is as follows: Y x端点 ’=∑y ix端点 ’;i=1,2…7,x 端点 =1,2,4; In the formula: Y x端点 'These are indicators for determining the degree of organic matter enrichment, specifically including Y1', Y2', and Y4'. y ix端点 'Let ' be the i-th evaluation index in x respectively 端点 The standardized values ​​of y when =1, 2, 4.

7. The characterization method for the enrichment control of source rock organic matter by tuff according to claim 6, characterized in that, The specific solution process for the target organic matter enrichment degree Y is as follows: Y=∑y ix '; In the formula: Y represents the enrichment degree of the target organic matter; y ix ' represents the standardized value of y corresponding to the i-th evaluation index and x.

8. The characterization method for the enrichment control of organic matter in source rocks by tuff according to claim 7, characterized in that, The specific process of standardization is as follows: and ix端点 '=(and ix端点 -and imin ) / (and imax -and imin ) and ix '=(and ix -and imin ) / (and imax -and imin ) In the formula: y ix端点 For the i-th evaluation index, respectively in x 端点 The y values ​​corresponding to =1,2,4; y imin Let y be the value of the i-th evaluation index when x=0.1; y imax The y-value is the value of the i-th evaluation index when the maximum value of the actual measured value of x=TOC is rounded up. y ix Let y be the y-value corresponding to x for the i-th evaluation index.

9. The characterization method for the control of organic matter enrichment in source rocks by tuff according to claim 1, characterized in that, The specific formulas for calculating the molybdenum enrichment coefficient and the uranium enrichment coefficient are as follows: Mo EF =(Mo 测量值 / To the 计算值 ) / (Mo PAAS / To the PAAS ); U EF =(U 测量值 / Al 计算值 ) / (U PAAS / Al PAAS ); In the formula: Mo 测量值 U 测量值 The values ​​are the measured contents of Mo and U elements in the rock sample, in grams; Al 计算值 The calculated content of Al in the rock sample is given in g; Mo... PAAS Al PAAS and U PAAS These are the average contents of Mo, Al, and U elements in Post-Archaeological Australian shale, in grams.

Images