Natural water-flooded oil layer identification method and related device

Abstract

The invention provides a natural water-flooded oil layer identification method and a related device. The method comprises the following steps: acquiring logging response characteristic parameters of a conventional oil layer, a poor oil layer, a natural water-flooded oil layer and a water layer of a coring well for constructing and adjusting an oil reservoir; calculating a natural potential relative value parameter and a resistivity ratio by using the logging response characteristic parameters; obtaining a boundary threshold value of the natural potential relative value parameter and the resistivity ratio by using the intersection distribution condition of the natural potential relative value parameter and the resistivity ratio; calculating a natural potential relative value parameter and a resistivity ratio of the non-cored well to be identified; and matching the natural potential relative value parameter and the resistivity ratio of the to-be-identified non-cored well with the boundary threshold, and identifying an oil layer, a poor oil layer, a natural water-flooded oil layer and a water layer of the non-cored well. The method is beneficial to accurately describing the oil-water interface form of the structure-adjusted oil reservoir, can improve the calculation precision of the original petroleum geological reserves of the structure-adjusted oil reservoir, and guides the optimization of an oil well perforation scheme.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and in particular relates to a natural water-flooded oil layer identification method and a related device. Background Art

[0002] Natural water-flooded oil layers refer to early oil reservoirs formed by the migration of oil and gas discharged from hydrocarbon-generating source rocks. Later orogenic movements caused early structures to tilt, and part of the oil in the early oil reservoirs was lost to form structurally adjusted oil reservoirs (oil fields). At the same time, formation water invaded some oil layers of structurally adjusted oil reservoirs (oil fields) to form natural water-flooded oil layers (water-flooded layers), and caused the oil-water interface of the structurally adjusted oil reservoirs (oil fields) to tilt.

[0003] Many oil reservoirs in my country's basins have experienced structural tilting, resulting in natural water flooding of oil layers and tilted oil-water interface. Many oil reservoirs abroad also have naturally water flooded oil layers and tilted oil-water interface.

[0004] In the early stage of structural adjustment reservoir (oil field) development, due to the limited data and people's understanding, natural water-flooded oil layers are often mistaken for poor oil layers, which leads to unreasonable oil well perforation, short water-free oil production period, low accuracy of original petroleum geological reserves calculation and other problems. There is an urgent need for a natural water-flooded layer identification technology to accurately and effectively identify natural water-flooded layers and oil layers. Summary of the invention

[0005] In order to effectively identify natural water-flooded oil layers and improve the prediction accuracy of oil well productivity and the calculation accuracy of original petroleum geological reserves, the present invention proposes a natural water-flooded oil layer identification method and related devices.

[0006] A method for identifying a natural water-flooded oil layer comprises the following steps:

[0007] Obtaining logging response characteristic parameters of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers of the core wells of the structural adjustment oil reservoir, wherein the logging response characteristic parameters at least include natural potential SP, deep resistivity Rt, shallow resistivity Rs and intrusion zone resistivity Rxo;

[0008] The logging response characteristic parameters are used to respectively calculate the natural potential relative value parameters and resistivity ratios of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers, wherein the natural potential relative value parameters are used to reflect the differences in natural potentials of conventional oil layers, water-flooded layers and water layers at different well points, and the resistivity ratio parameters are used to reflect the differences in the distribution of resistivity values ​​and the changing laws of the ratios among conventional oil layers, poor oil layers, water-flooded layers and water layers;

[0009] Using the intersection distribution of the natural potential relative value parameter and the resistivity ratio, the boundary thresholds of the natural potential relative value parameter and the resistivity ratio of the conventional oil layer, the poor oil layer, the natural water-flooded oil layer and the water layer are obtained;

[0010] Obtaining logging response characteristic parameters of the non-coring well to be identified, and calculating the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified;

[0011] The natural potential relative value parameters and resistivity ratio of the non-coring well to be identified are matched with the demarcation threshold to identify the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the non-coring well.

[0012] Furthermore, before obtaining the logging response characteristic parameters of the conventional oil layer, the poor oil layer, the natural water-flooded oil layer and the water layer of the coring well of the structural adjustment oil reservoir, the following steps are also included:

[0013] A coring well of a structural adjustment oil reservoir is selected, wherein the coring well includes a natural water-flooded layer, and conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers are determined according to the core display characteristics.

[0014] Further, the calculating of the natural potential relative value parameter by using the logging response characteristic parameter includes calculating the natural potential relative value parameter according to a preset first formula:

[0015]

[0016] Where: RSP represents the relative value of natural potential SP, SP max , SP min They represent the natural potential value at any point and the maximum and minimum natural potential of the target layer respectively.

[0017] Further, the calculating the resistivity ratio by using the logging response characteristic parameter includes calculating the resistivity ratio according to a preset second formula:

[0018]

[0019] Where: RR represents the relative value of resistivity, R t , R s , R xo They represent the deep resistivity, shallow resistivity and intrusion zone resistivity of the formation respectively.

[0020] Furthermore, the calculation of the relative value parameters of the natural potential and the resistivity ratio of the non-coring well to be identified includes:

[0021] Obtain the natural potential SP, deep resistivity Rt, shallow resistivity Rs, and intrusion zone resistivity Rxo of the non-coring well to be identified;

[0022] The relative value parameter of the natural potential is obtained using the preset first formula, and the resistivity ratio is obtained using the preset second formula.

[0023] Furthermore, the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified are matched with the demarcation threshold to identify the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well, and also includes the need to combine natural gamma and deep formation resistivity to distinguish conventional oil layers from poor oil layers.

[0024] On the other hand, the present invention also discloses a method for identifying a natural water-flooded oil layer, comprising the following steps:

[0025] Acquire logging response characteristic parameters of the non-coring well to be identified, and calculate the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified, wherein the logging response characteristic parameters at least include natural potential, deep resistivity, shallow resistivity, and intrusion zone resistivity;

[0026] The natural potential relative value parameters and resistivity ratio of the non-coring well to be identified are matched with the preset demarcation threshold to identify the conventional oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well. The preset demarcation threshold is the natural potential relative value parameters and resistivity ratio that the conventional oil layer, poor oil layer, natural water-flooded oil layer and water layer need to meet simultaneously.

[0027] In a third aspect, the present invention further discloses a natural water-flooded oil layer identification device, comprising a logging response characteristic parameter acquisition module, a first calculation module, a demarcation threshold generation module, a second calculation module, and an identification module, wherein:

[0028] A logging response characteristic parameter acquisition module is used to obtain the logging response characteristic parameters of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers of the coring wells of the structural adjustment oil reservoir, wherein the logging response characteristic parameters at least include natural potential SP, deep resistivity Rt, shallow resistivity Rs and intrusion zone resistivity Rxo;

[0029] The first calculation module is used to calculate the natural potential relative value parameters and resistivity ratios of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers respectively by using the logging response characteristic parameters, wherein the natural potential relative value parameters are used to reflect the differences in natural potentials of conventional oil layers, water-flooded layers and water layers at different well points, and the resistivity ratio parameters are used to reflect the differences in the distribution of resistivity values ​​and the changing laws of the ratios among conventional oil layers, poor oil layers, water-flooded layers and water layers;

[0030] The demarcation threshold generation block is used to obtain the demarcation thresholds of the natural potential relative value parameters and the resistivity ratio of the conventional oil layer, the poor oil layer, the natural water-flooded oil layer and the water layer by using the intersection distribution of the natural potential relative value parameters and the resistivity ratio;

[0031] The second calculation module is used to calculate the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified;

[0032] The identification module is used to match the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified with the boundary threshold to identify the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the non-coring well.

[0033] Based on the above technical solution, the beneficial effects of the present invention compared with the prior art are as follows:

[0034] According to the similarities and differences between natural water-flooded oil layers and poor oil layers, the present invention calculates the demarcation thresholds of natural potential relative value parameters and resistivity ratios for conventional oil layers, poor oil layers, natural water-flooded oil layers, and water layers based on natural potential and resistivity logging responses; then the natural potential relative value parameters and resistivity ratios of the non-coring wells to be identified are matched with the demarcation thresholds, and the oil layers, poor oil layers, natural water-flooded oil layers, and water layers of the non-coring wells can be effectively identified. The present invention is conducive to accurately describing the oil-water interface morphology of the structurally adjusted oil reservoir, can improve the calculation accuracy of the original petroleum geological reserves of the structurally adjusted oil reservoir, and guide the optimization of the oil well perforation scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 This is a flow chart of a method for identifying a natural water-flooded oil layer in Embodiment 1 of the present invention;

[0037] Figure 2 This is a core schematic diagram of a conventional oil layer, a poor oil layer, a natural water-flooded oil layer and a water layer in Example 1 of the present invention;

[0038] Figure 3 The comprehensive histogram of a well in the first embodiment of the present invention;

[0039] Figure 4 The intersection diagram of the relative value of spontaneous potential RSP and the resistivity ratio RR of a certain oil field in the first embodiment of the present invention;

[0040] Figure 5 This is a flow chart of another method for identifying natural water-flooded oil layers in Embodiment 2 of the present invention;

[0041] Figure 6 This is a schematic structural diagram of a natural water-flooded oil layer identification device in Embodiment 3 of the present invention;

[0042] Figure 7This is a schematic structural diagram of another natural water-flooded oil layer identification device in the fourth embodiment of the present invention. DETAILED DESCRIPTION

[0043] The inventors have found through extensive research that structural adjustment reservoirs are formed in advance, and the subsequent orogenic movement causes structural tilting, resulting in formation water displacing part of the oil layer, forming a natural water-flooded oil layer (water-flooded layer). Therefore, inside the structural adjustment reservoir, there are conventional oil layers, poor oil layers, natural water-flooded oil layers, and water layers. In the case of relatively little data and limited knowledge, natural water-flooded oil layers are easily misjudged as poor oil layers, resulting in unreasonable perforation of oil wells, a short water-free oil production period, and low calculation accuracy of original petroleum geological reserves.

[0044] The natural water-flooded oil layer and the poor oil layer in the structural adjustment reservoir have certain similarities. The common points between the two are mainly manifested in the following aspects: First, the deep resistivity logging values ​​are both low. The formation resistivity of both is lower than that of conventional oil layers, but higher than that of water layers. Overall, they both show the characteristics of relatively low deep resistivity. Second, the oil saturation is low. According to the calculation of the oil saturation logging interpretation formula, the oil saturation of both is generally lower than that of conventional oil layers.

[0045] Although natural water-flooded oil layers and poor oil layers have certain similarities, their differences are also very obvious. The differences between the two are mainly manifested in the following five aspects: First, the formation mechanism is different. Natural water-flooded oil layers are due to the structural tilting of the orogenic movement, and the formation water displaces part of the oil layer, resulting in low oil saturation and low resistivity; while poor oil layers have low oil saturation and low resistivity due to low porosity and permeability. Second, the core intuitive display is different. The core of the poor oil layer is a low oil-containing grade such as oil immersion or oil spots, and the oil content is uneven, but the core contains only oil and no water, and the water drops are "spherical". The color of the core is basically the same as that of conventional oil layers; natural water-flooded oil layers show the characteristics of "water flooding", the core contains both oil and water, the water drops are "hemispherical" or rapidly penetrated, and the color of the core is dark brown, which is darker than the color of conventional oil layers. The third is the different logging response. The natural potential characteristics of the poor oil layer are similar to those of the oil layer, and the resistivity is relatively high; while the natural potential curve characteristics of the natural water-flooded oil layer are similar to those of the water-flooded layer, and the resistivity is relatively low. Among them, the first and second points are the basis of the third point. From two other perspectives, the inventors also found two differences, namely, the fourth is the different spatial positions of the distribution. Poor oil layers are generally distributed between conventional oil layers, while natural water-flooded oil layers generally appear at the bottom of conventional oil layers, located at the top of the "bottom water" or "oil-water transition zone" of the ancient oil reservoir. The fifth is the different production capacity. The porosity and permeability of the poor oil layer are low. Although its production capacity is low, it generally does not produce water; the production capacity of the natural water-flooded layer is relatively high, but its water production rate is relatively high, and the oil production is low or even no oil is produced.

[0046] According to the similarities and differences between natural water-flooded oil layers and poor oil layers, the inventors found that the difference based on the third point is relatively easy to quantify, and therefore proposed a method for identifying natural water-flooded oil layers.

[0047] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0048] Embodiment 1

[0049] A natural water-flooded oil layer identification method, combined with Figure 1 As shown, steps S110-S150 are included, specifically:

[0050] Step S110, obtaining logging response characteristic parameters of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers of the core wells of the structural adjustment oil reservoir, wherein the logging response characteristic parameters at least include natural potential SP, deep resistivity Rt, shallow resistivity Rs and invasion zone resistivity Rxo.

[0051] Combination Figure 3 As shown, specifically, the logging response characteristic parameters of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers can be directly obtained through open hole logging, where:

[0052] The natural potential SP of conventional oil layers shows a large negative anomaly. Although the resistivity Rxo of the invasion zone is relatively high, there is a large positive difference between it and the shallow resistivity Rs curve and the deep resistivity Rt curve. The resistivity Rxo of the invasion zone, the shallow resistivity Rs curve and the deep resistivity Rt satisfy the following relationship: Rt>Rs>>Rxo, and the shallow resistivity Rs curve and the deep resistivity Rt are both relatively large.

[0053] The natural potential SP of the poor oil layer shows a large negative anomaly, and the resistivity of the invasion zone (Rxo) is still relatively high, but it still shows a low-amplitude positive difference with the shallow resistivity (Rs) curve and the deep resistivity (Rt) curve; the deep resistivity and shallow resistivity values ​​are lower than those of conventional oil layers, and there is a small positive difference between the two. The resistivity Rxo of the invasion zone, the shallow resistivity Rs curve and the deep resistivity Rt satisfy the following relationship: Rt>Rs>Rxo.

[0054] The natural potential of the natural water-flooded oil layer is negatively abnormal, but compared with conventional oil layers or poor oil layers, its abnormal amplitude is relatively low; its deep resistivity value Rt, shallow resistivity value Rs and invasion zone resistivity value Rxo are all significantly lower than those of conventional oil layers or poor oil layers, the deep resistivity Rt and shallow resistivity Rs curves are basically close, and there is a low-amplitude positive difference between them and the shallow resistivity (Rs) curve, and its invasion zone resistivity Rxo, shallow resistivity Rs curve and deep resistivity Rt satisfy the following relationship: Rt≈Rs>Rxo.

[0055] The formation water in the water layer has high mineralization and strong conductivity. The resistivity of the water layer is less than 1Ω.m. Its deep resistivity and shallow resistivity are slightly lower than the resistivity of the invasion zone, and the overall resistance is increased, but the three are basically similar. The resistivity Rxo of the invasion zone, the shallow resistivity Rs curve and the deep resistivity Rt satisfy the following relationship: Rt≈Rs <Rxo。

[0056] It is understandable that before this step, it is necessary to determine the conventional oil layer, poor oil layer, and natural water-flooded oil layer of the coring well based on the core display characteristics. According to the difference in fluids contained in the underground reservoir and the reservoir quality, the oil and water layers of the structurally adjusted reservoir (oil field) are divided into oil layers, poor oil layers, natural water-flooded oil layers, and water layers. A reservoir with good reservoir quality and saturated with oil is an oil layer; a reservoir with poor reservoir quality and relatively low oil saturation is a poor oil layer; an oil layer with good reservoir quality and part of which is displaced by formation water due to tectonic movement is a natural water-flooded oil layer; a reservoir that is always saturated with formation water is a water layer. Specifically, combined with Figure 2 As shown in the figure, a typical system coring well of the structural adjustment reservoir was selected to observe the core display characteristics of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers. The core of the conventional oil layer is light brown, with relatively high porosity and relatively small changes; it is mainly rich in oil and saturated with oil, and the water drop is spherical. The core of the poor oil layer is also light brown, and the lithology and physical properties vary greatly. The area with relatively high porosity is mainly oil-immersed, and the water drop is spherical; the area with small porosity and relatively poor physical properties has poor oil content or no oil, and the oil content is unevenly distributed. The core of the natural water-flooded oil layer has relatively high porosity and relatively good physical properties, but the oil content is not saturated, mainly oil spots, mainly dark brown, and the water drop quickly penetrates or is hemispherical, showing the hydrophilic characteristics of the rock. The core of the water layer is basically oil-free, grayish white, strongly hydrophilic, and quickly penetrates after dripping water.

[0057] In this step, the oil layer, poor oil layer, natural water-flooded oil layer and water layer are identified according to the oil content, reservoir properties and formation mechanism of various oil and water layers shown in the core of the coring well; and the corresponding relationship between the natural potential SP, deep resistivity Rt, shallow resistivity Rs, invaded zone resistivity Rxo and other logging response parameter characteristics of the oil layer, poor oil layer, natural water-flooded oil layer and water layer are established through the logging response characteristic parameters obtained by open hole logging.

[0058] Step S120, using the logging response characteristic parameters to respectively calculate the natural potential relative value parameters and resistivity ratios of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers, wherein the natural potential relative value parameters are used to reflect the differences in natural potentials of conventional oil layers, water-flooded layers and water layers at different well points, and the resistivity ratio parameters are used to reflect the differences in the distribution of resistivity values ​​and the changing rules of the ratios among conventional oil layers, poor oil layers, water-flooded layers and water layers.

[0059] It can be understood by those skilled in the art that when there is a difference in pressure and mineralization between formation water and drilling fluid, it will cause anions and cations to diffuse in different directions and rock particles to adsorb ions differently, thereby generating diffusion electromotive force and adsorption electromotive force near the well wall, forming a natural electric field. Natural potential logging is a type of logging that measures the natural electric field potential generated by each rock layer during drilling. The measured potential value only indicates the relative height of the natural potential, and there is no absolute zero line.

[0060] In order to quantitatively reflect the differences in natural potentials of oil layers, flooded layers and water layers at different well points, the relative value of natural potential (RSP) parameter is introduced, and its expression is the preset first formula:

[0061]

[0062] Where: RSP represents the relative value of the natural potential, dimensionless, and its value ranges from 0 to 1, SP, SP max , SP min They represent the natural potential value at any point, the maximum and minimum natural potential of the target layer, mV respectively.

[0063] Since the measured value of the natural potential of the oil layer is closer to the minimum value of the natural potential, and the measured value of the natural potential of the water-flooded layer and the water layer is closer to the maximum value of the natural potential, after the above data transformation processing, the RSP value of the oil layer is close to 1, while the RSP value of the water-flooded layer and the water layer is closer to 0. This formula converts the natural potential values ​​measured at different well points into relative values ​​of natural potential between 0 and 1, which is dimensionless, thereby eliminating the influence of logging instruments, logging environment, etc. on the natural potential logging response.

[0064] In addition, the inventors found that the amplitude differences Rt / Rxo and Rs / Rxo between the deep resistivity Rt, the shallow resistivity Rs and the intrusion zone resistivity Rxo are different among oil layers, poor oil layers, water-flooded layers and water layers. Taking into account the distribution of resistivity values ​​and the changing law of their ratios, the resistivity ratio parameter RR can better reflect the differences among oil layers, poor oil layers, water-flooded layers and water layers. The specific calculation formula is the preset second formula:

[0065]

[0066] Where: RR represents the relative value of resistivity, dimensionless, RR t , R s , R xo They represent the deep resistivity, shallow resistivity and intrusion zone resistivity of the stratum respectively, unit: Ω.m.

[0067] Step S130, using the intersection distribution of the natural potential relative value parameter and the resistivity ratio, obtain the boundary thresholds of the natural potential relative value parameter and the resistivity ratio for conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers.

[0068] Based on the intersection diagram and data statistics of the relative value of natural potential RSP and the resistivity ratio RR of various oil-water layers, the classification boundaries of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers are clearly defined.

[0069] Combination Figure 4 As shown in the figure, the distribution range of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers on the intersection diagram of natural potential relative value RSP and resistivity ratio RR is obviously different. Conventional oil layers and poor oil layers are distributed in the upper right corner of the intersection diagram. Although there are overlapping parts between the two, there are still obvious differences between them and water-flooded layers, which are mainly reflected in: the natural potential relative value RSP of oil layers and poor oil layers is greater than 0.5 and 0.44 respectively, while the natural potential relative value RSP of water-flooded layers is between 0.12 and 0.44; the resistivity ratio RR of oil layers and poor oil layers is greater than 0.5, while the resistivity ratio RR of water-flooded layers is between 0 and 1. For the same well, the deep resistivity value Rt of water-flooded layers is lower than that of poor oil layers, so it is easier to distinguish. The natural potential relative value RSP of water layers is less than 0.12, and the resistivity ratio RR is less than 0. The values ​​of the two characteristic parameters are relatively low, which is easy to identify. Table 1 shows the demarcation thresholds of natural potential relative value parameters and resistivity ratios for conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers.

[0070] Step S140, obtaining the logging response characteristic parameters of the non-coring well to be identified, and calculating the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified.

[0071] Specifically, the natural potential SP, deep resistivity Rt, shallow resistivity Rs, and intrusion zone resistivity Rxo of the non-coring well to be identified are obtained; the natural potential relative value parameter is obtained using the preset first formula, and the resistivity ratio is obtained using the preset second formula.

[0072] Preset the first formula:

[0073]

[0074] Where: RSP represents the relative value of the natural potential, dimensionless, and its value ranges from 0 to 1, SP, SP max , SP min They represent the natural potential value at any point, the maximum and minimum natural potential of the target layer, mV respectively.

[0075] Preset the second formula:

[0076]

[0077] Where: RR represents the relative value of resistivity, dimensionless, R t , R s , R xo They represent the deep resistivity, shallow resistivity and intrusion zone resistivity of the stratum respectively, unit: Ω.m.

[0078] Step S150, using the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified to match the boundary threshold, the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well are identified.

[0079] The natural potential relative value parameters and resistivity ratio of the non-coring well to be identified are matched with the demarcation thresholds in Table 1 to identify the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well.

[0080] By using the method of the embodiment of the present invention, the inventors effectively identified conventional oil layers, poor oil layers and water-flooded layers in six oil wells including a well in a certain oil field. The oil layer classification results were verified by actual production tests, which effectively guided the optimization of the oil well perforation scheme and the prediction of the oil-water interface in the oil field.

[0081] In some embodiments, the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified are matched with the demarcation threshold value to identify the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well. Then, the natural gamma and deep formation resistivity are combined to distinguish the conventional oil layer and the poor oil layer. Therefore, the natural gamma logging value needs to be obtained during well logging. The main characteristics of these two types of oil layers are:

[0082] Conventional oil layers have relatively low natural gamma values ​​and high deep resistivity, with natural gamma logging values ​​ranging from 7.8 to 18.5 API, with an average of 12.2 API; deep resistivity logging values ​​ranging from 398.8 to 595 Ω.m, with an average of 146 Ω.m. Poor oil layers have relatively high natural gamma values ​​and low deep resistivity, with natural gamma logging values ​​ranging from 19.8 to 37 API, with an average of 25 API; deep resistivity logging values ​​ranging from 48 to 125 Ω.m, with an average of 73.6 Ω.m.

[0083] According to the similarities and differences between natural water-flooded oil layers and poor oil layers, the present invention calculates the natural potential relative value RSP and the resistivity ratio RR based on the natural potential and resistivity logging response. The poor oil layer and the natural water-flooded oil layer can be quickly distinguished through the intersection diagram of RSP and RR or the numerical value between the two.

[0084] Accurately identifying natural water-flooded oil reservoirs has the following advantages:

[0085] (1) It is conducive to accurately describing the morphology of the oil-water interface in the structural adjustment reservoir. Natural water-flooded oil layers generally appear at the bottom of the structural adjustment reservoir, and there is a "new" oil-water interface between the oil layer and the natural water-flooded oil layer. Due to the difference in structural adjustment intensity and the change in structural spatial position, the thickness of the natural water-flooded oil layer at different well points in the structural adjustment reservoir varies. Based on the identification of natural water-flooded oil layers at each well point, the spatial morphology of the oil-water interface can be quantitatively characterized, and then the occurrence of the oil-water interface can be clarified, providing a basis for the calculation of original petroleum geological reserves and perforation optimization.

[0086] (2) It is helpful to improve the calculation accuracy of the original geological reserves of petroleum in the structural adjustment reservoir. Since the present invention effectively distinguishes between poor oil layers and natural water-flooded oil layers, the thickness of the natural water-flooded oil layers can be effectively eliminated when calculating the original geological reserves of petroleum. At the same time, the present invention can accurately describe that the oil-water interface of the structural adjustment reservoir is inclined rather than horizontal, so the calculation accuracy of the oil volume in the structural adjustment reservoir can be improved. The above two aspects show that accurate identification of natural water-flooded oil layers is an important guarantee for accurately calculating the original geological reserves of petroleum in the structural adjustment reservoir.

[0087] (3) It can guide the optimization of oil well perforation schemes. The present invention can effectively identify the natural water-flooded oil layer and the oil-water interface morphology, and can guide the optimization of oil well perforation sections to avoid mis-shooting the natural water-flooded oil layer. By rationally optimizing the avoidance height of the oil well, the waterless production period of the oil well can be extended, and the development effect of the oil well can be improved to the maximum extent.

[0088] Embodiment 2

[0089] In other embodiments, it is not necessary to execute step S110 to step S130 in embodiment 1 every time, and the previously obtained demarcation threshold can be directly used to identify the natural water-flooded oil layer.

[0090] like Figure 5 As shown, a method for identifying a natural water-flooded oil layer includes steps S210 and S220:

[0091] Step S210, obtaining the logging response characteristic parameters of the non-coring well to be identified, and calculating the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified, wherein the logging response characteristic parameters at least include natural potential, deep resistivity, shallow resistivity, and intrusion zone resistivity.

[0092] The natural potential SP, deep resistivity Rt, shallow resistivity Rs, and intrusion zone resistivity Rxo of the non-coring well to be identified can be directly obtained through open hole logging; the natural potential relative value parameter is obtained using the preset first formula, and the resistivity ratio is obtained using the preset second formula.

[0093] Preset the first formula:

[0094]

[0095] Where: RSP represents the relative value of the natural potential, dimensionless, and its value ranges from 0 to 1, SP, SP max , SP min They represent the natural potential value at any point, the maximum and minimum natural potential of the target layer, mV respectively.

[0096] Preset the second formula:

[0097]

[0098] Where: RR represents the relative value of resistivity, dimensionless, R t , R s , R xo They represent the deep resistivity, shallow resistivity and intrusion zone resistivity of the stratum respectively, unit: Ω.m.

[0099] Step S220, using the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified to match with the preset demarcation threshold, the conventional oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well are identified. The preset demarcation threshold is the natural potential relative value parameters and resistivity ratio that the conventional oil layer, poor oil layer, natural water-flooded oil layer and water layer need to meet simultaneously.

[0100] The preset demarcation threshold can be as shown in Table 1, the RSP of the poor oil layer>0.44, and the RR value>0.5; while the RSP of the natural water-flooded oil layer<0.44, and the RR value is between 0 and 1. In this embodiment, it is also necessary to distinguish between conventional oil layers and poor oil layers in combination with natural gamma and deep formation resistivity. Specifically, it is also necessary to obtain natural gamma logging values ​​when logging. The natural gamma value of conventional oil layers is relatively low and the deep resistivity is large. Its natural gamma logging value is distributed between 7.8 and 18.5 API, with an average of 12.2 API; the deep resistivity logging value is distributed between 398.8 and 595 Ω.m, with an average of 146 Ω.m. The natural gamma value of the poor oil layer is relatively high and the deep resistivity is relatively small. Its natural gamma logging value is distributed between 19.8 and 37 API, with an average of 25 API; the deep resistivity logging value is distributed between 48 and 125 Ω.m, with an average of 73.6 Ω.m.

[0101] Embodiment 3

[0102] The present invention also discloses a natural water-flooded oil layer identification device, combined with Figure 6 As shown, it includes a logging response characteristic parameter acquisition module 10, a first calculation module 20, a demarcation threshold generation module 30, a second calculation module 40, and an identification module 50, wherein:

[0103] The logging response characteristic parameter acquisition module 10 is used to obtain the logging response characteristic parameters of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers in the core wells of the structural adjustment oil reservoir, and the logging response characteristic parameters at least include natural potential SP, deep resistivity Rt, shallow resistivity Rs, and invasion zone resistivity Rxo.

[0104] Specifically, the logging response characteristic parameters of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers can be directly obtained through open hole logging, including:

[0105] The natural potential SP of conventional oil layers shows a large negative anomaly. Although the resistivity Rxo of the invasion zone is relatively high, there is a large positive difference between it and the shallow resistivity Rs curve and the deep resistivity Rt curve. The resistivity Rxo of the invasion zone, the shallow resistivity Rs curve and the deep resistivity Rt satisfy the following relationship: Rt>Rs>>Rxo, and the shallow resistivity Rs curve and the deep resistivity Rt are both relatively large.

[0106] The natural potential SP of the poor oil layer shows a large negative anomaly, and the resistivity of the invasion zone (Rxo) is still relatively high, but it still shows a low-amplitude positive difference with the shallow resistivity (Rs) curve and the deep resistivity (Rt) curve; the deep resistivity and shallow resistivity values ​​are lower than those of conventional oil layers, and there is a small positive difference between the two. The resistivity Rxo of the invasion zone, the shallow resistivity Rs curve and the deep resistivity Rt satisfy the following relationship: Rt>Rs>Rxo.

[0107] The natural potential of the natural water-flooded oil layer is negatively abnormal, but compared with conventional oil layers or poor oil layers, its abnormal amplitude is relatively low; its deep resistivity value Rt, shallow resistivity value Rs and invasion zone resistivity value Rxo are all significantly lower than those of conventional oil layers or poor oil layers, the deep resistivity Rt and shallow resistivity Rs curves are basically close, and there is a low-amplitude positive difference between them and the shallow resistivity (Rs) curve, and its invasion zone resistivity Rxo, shallow resistivity Rs curve and deep resistivity Rt satisfy the following relationship: Rt≈Rs>Rxo.

[0108] The formation water in the water layer has high mineralization and strong conductivity. The resistivity of the water layer is less than 1Ω.m. Its deep resistivity and shallow resistivity are slightly lower than the resistivity of the invasion zone, and the overall resistance is increased, but the three are basically similar. The resistivity Rxo of the invasion zone, the shallow resistivity Rs curve and the deep resistivity Rt satisfy the following relationship: Rt≈Rs <Rxo。

[0109] The first calculation module 20 is used to calculate the natural potential relative value parameters and resistivity ratios of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers respectively using the logging response characteristic parameters, wherein the natural potential relative value parameters are used to reflect the differences in natural potentials of conventional oil layers, water-flooded layers and water layers at different well points, and the resistivity ratio parameters are used to reflect the differences in the distribution of resistivity values ​​and the changing laws of the ratios between conventional oil layers, poor oil layers, water-flooded layers and water layers.

[0110] In order to quantitatively reflect the differences in natural potentials of oil layers, flooded layers and water layers at different well points, the relative value of natural potential (RSP) parameter is introduced, and its expression is the preset first formula:

[0111]

[0112] Where: RSP represents the relative value of the natural potential, dimensionless, and its value ranges from 0 to 1, SP, SP max , SP min They represent the natural potential value at any point, the maximum and minimum natural potential of the target layer, mV respectively.

[0113] Since the measured value of the natural potential of the oil layer is closer to the minimum value of the natural potential, and the measured value of the natural potential of the water-flooded layer and the water layer is closer to the maximum value of the natural potential, after the above data transformation processing, the RSP value of the oil layer is close to 1, while the RSP value of the water-flooded layer and the water layer is closer to 0. This formula converts the natural potential values ​​measured at different well points into relative values ​​of natural potential between 0 and 1, which is dimensionless, thereby eliminating the influence of logging instruments, logging environment, etc. on the natural potential logging response.

[0114] In addition, the inventors found that the amplitude differences Rt / Rxo and Rs / Rxo between the deep resistivity Rt, the shallow resistivity Rs and the intrusion zone resistivity Rxo are different among oil layers, poor oil layers, water-flooded layers and water layers. Taking into account the distribution of resistivity values ​​and the changing law of their ratios, the resistivity ratio parameter RR can better reflect the differences among oil layers, poor oil layers, water-flooded layers and water layers. The specific calculation formula is the preset second formula:

[0115]

[0116] Where: RR represents the relative value of resistivity, dimensionless, R t , R s , R xo They represent the deep resistivity, shallow resistivity and intrusion zone resistivity of the stratum respectively, unit: Ω.m.

[0117] The demarcation threshold generation module 30 is used to obtain the demarcation thresholds of the natural potential relative value parameters and resistivity ratios of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers by using the intersection distribution of the natural potential relative value parameters and resistivity ratios.

[0118] Based on the intersection diagram and data statistics of the relative value of natural potential RSP and the resistivity ratio RR of various oil-water layers, the classification boundaries of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers are clearly defined.

[0119] Combination Figure 4 As shown in the figure, the distribution ranges of conventional oil layers, poor oil layers, water-flooded layers and water layers on the intersection diagram of the relative value of natural potential RSP and the resistivity ratio RR are significantly different. Conventional oil layers and poor oil layers are distributed in the upper right corner of the intersection diagram. Although there are overlapping parts between the two, there are still obvious differences between them and the water-flooded layers, which are mainly reflected in: the relative value of natural potential RSP of oil layers and poor oil layers is greater than 0.5 and 0.44 respectively, while the relative value of natural potential RSP of water-flooded layers is between 0.12 and 0.44; the resistivity ratio RR of oil layers and poor oil layers is greater than 0.5, while the resistivity ratio RR of water-flooded layers is between 0 and 1. For the same well, the deep resistivity value Rt of water-flooded layers is lower than that of poor oil layers, so it is easier to distinguish. The relative value of natural potential RSP of water layers is less than 0.12, and the resistivity ratio RR is less than 0. The values ​​of the two characteristic parameters are relatively low, which is easy to identify. Table 1 shows the demarcation thresholds of natural potential relative value parameters and resistivity ratios for conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers.

[0120] The second calculation module 40 is used to obtain the logging response characteristic parameters of the non-coring well to be identified, and calculate the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified.

[0121] Specifically, the natural potential SP, deep resistivity Rt, shallow resistivity Rs, and intrusion zone resistivity Rxo of the non-coring well to be identified are obtained; the natural potential relative value parameter is obtained using the preset first formula, and the resistivity ratio is obtained using the preset second formula.

[0122] Preset the first formula:

[0123]

[0124] Where: RSP represents the relative value of the natural potential, dimensionless, and its value ranges from 0 to 1, SP, SP max , SP min They represent the natural potential value at any point, the maximum and minimum natural potential of the target layer, mV respectively.

[0125] Preset the second formula:

[0126]

[0127] Where: RR represents the relative value of resistivity, dimensionless, R t , R s , R xo They represent the deep resistivity, shallow resistivity and intrusion zone resistivity of the stratum respectively, unit: Ω.m.

[0128] The identification module 50 is used to identify the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the non-coring well by matching the natural potential relative value parameters and resistivity ratio of the non-coring well to the boundary threshold.

[0129] The natural potential relative value parameters and resistivity ratio of the non-coring well to be identified are matched with the demarcation thresholds in Table 1 to identify the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well.

[0130] According to the similarities and differences between natural water-flooded oil layers and poor oil layers, the present invention calculates the demarcation thresholds of natural potential relative value parameters and resistivity ratios for conventional oil layers, poor oil layers, natural water-flooded oil layers, and water layers based on natural potential and resistivity logging responses; then the natural potential relative value parameters and resistivity ratios of the non-coring wells to be identified are matched with the demarcation thresholds, and the oil layers, poor oil layers, natural water-flooded oil layers, and water layers of the non-coring wells can be effectively identified. The present invention is conducive to accurately describing the oil-water interface morphology of the structurally adjusted oil reservoir, can improve the calculation accuracy of the original petroleum geological reserves of the structurally adjusted oil reservoir, and guide the optimization of the oil well perforation scheme.

[0131] Embodiment 4

[0132] Corresponding to the second embodiment, the embodiment of the present invention also discloses a natural water-flooded oil layer identification device, combined with Figure 7 As shown, it includes a calculation module 10' and an identification module 20', wherein:

[0133] The calculation module 10' is used to obtain the logging response characteristic parameters of the non-coring well to be identified, and calculate the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified. The logging response characteristic parameters at least include natural potential, deep resistivity, shallow resistivity, and intrusion zone resistivity.

[0134] The natural potential SP, deep resistivity Rt, shallow resistivity Rs, and intrusion zone resistivity Rxo of the non-coring well to be identified are obtained by open hole logging; the natural potential relative value parameter is obtained by the preset first formula, and the resistivity ratio is obtained by the preset second formula.

[0135] Preset the first formula:

[0136]

[0137] Where: RSP represents the relative value of the natural potential, dimensionless, and its value ranges from 0 to 1, SP, SP max , SP min They represent the natural potential value at any point, the maximum and minimum natural potential of the target layer, mV respectively.

[0138] Preset the second formula:

[0139]

[0140] Where: RR represents the relative value of resistivity, dimensionless, R t , R s , R xo They represent the deep resistivity, shallow resistivity and intrusion zone resistivity of the stratum respectively, unit: Ω.m.

[0141] The identification module 20' is used to match the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified with the preset demarcation threshold value to identify the conventional oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well. The preset demarcation threshold value is the natural potential relative value parameters and resistivity ratio that the conventional oil layer, poor oil layer, natural water-flooded oil layer and water layer need to meet simultaneously.

[0142] The natural potential relative value parameters and resistivity ratio of the non-coring well to be identified are matched with the demarcation thresholds in Table 1 to identify the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well.

[0143] In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly stated in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0144] The above description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is encompassed in a manner similar to the term "including", as explained by "including," used as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

Claims

1. A method for identifying a natural water-flooded oil layer, characterized in that: The following steps are involved: Obtaining logging response characteristic parameters of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers of core wells of structural adjustment oil reservoirs, wherein the logging response characteristic parameters at least include natural potential, deep resistivity, shallow resistivity and intrusion zone resistivity; The logging response characteristic parameters are used to respectively calculate the natural potential relative value parameters and resistivity ratios of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers, wherein the natural potential relative value parameters are used to reflect the differences in natural potentials of conventional oil layers, water-flooded layers and water layers at different well points, and the resistivity ratio parameters are used to reflect the differences in the distribution of resistivity values ​​and the changing laws of the ratios among conventional oil layers, poor oil layers, water-flooded layers and water layers; Using the intersection distribution of the natural potential relative value parameter and the resistivity ratio, the boundary thresholds of the natural potential relative value parameter and the resistivity ratio of the conventional oil layer, the poor oil layer, the natural water-flooded oil layer and the water layer are obtained; Obtaining logging response characteristic parameters of the non-coring well to be identified, and calculating the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified; The natural potential relative value parameters and resistivity ratio of the non-coring well to be identified are matched with the demarcation threshold to identify the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the non-coring well.

2. The method for identifying a natural water-flooded oil layer according to claim 1, characterized in that: Before obtaining the logging response characteristic parameters of the conventional oil layer, the poor oil layer, the natural water-flooded oil layer and the water layer of the coring well of the structural adjustment oil reservoir, the following steps are also included: A coring well of a structural adjustment oil reservoir is selected, wherein the coring well includes a natural water-flooded layer, and conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers are determined according to the core display characteristics.

3. The method for identifying a natural water-flooded oil layer according to claim 1, characterized in that: The calculating of the relative value parameter of the natural potential by using the logging response characteristic parameter comprises calculating the relative value parameter of the natural potential according to a preset first formula: Where: RSP represents the relative value of natural potential SP, SP max , SP min They represent the natural potential value at any point and the maximum and minimum natural potential of the target layer respectively.

4. The method for identifying a natural water-flooded oil layer according to claim 3, characterized in that: The method of calculating the resistivity ratio by using the logging response characteristic parameter includes calculating the resistivity ratio according to a preset second formula: Where: RR represents the relative value of resistivity, R t , R s , R xo They represent the deep resistivity, shallow resistivity and intrusion zone resistivity of the formation respectively.

5. The method for identifying a natural water-flooded oil layer according to claim 4, characterized in that: The calculation of the relative value parameters of the spontaneous potential and the resistivity ratio of the non-coring well to be identified includes: Obtain the natural potential, deep resistivity, shallow resistivity, and intrusion zone resistivity of the non-coring well to be identified; The relative value parameter of the natural potential is obtained using the preset first formula, and the resistivity ratio is obtained using the preset second formula.

6. The method for identifying a natural water-flooded oil layer according to claim 1, characterized in that: The natural potential relative value parameters and resistivity ratio of the non-coring well to be identified are matched with the demarcation threshold to identify the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well, and also includes the need to combine natural gamma and deep formation resistivity to distinguish conventional oil layers from poor oil layers.

7. A method for identifying a natural water-flooded oil layer, characterized in that: The following steps are involved: Acquire logging response characteristic parameters of the non-coring well to be identified, and calculate the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified, wherein the logging response characteristic parameters at least include natural potential, deep resistivity, shallow resistivity, and intrusion zone resistivity; The natural potential relative value parameters and resistivity ratio of the non-coring well to be identified are matched with the preset demarcation threshold to identify the conventional oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well. The preset demarcation threshold is the natural potential relative value parameters and resistivity ratio that the conventional oil layer, poor oil layer, natural water-flooded oil layer and water layer need to meet simultaneously.

8. The method for identifying a natural water-flooded oil layer according to claim 7, characterized in that: The calculation of the relative value parameters of the spontaneous potential and the resistivity ratio of the non-coring well to be identified includes: The relative value parameter of the natural potential is obtained by using a preset first formula, and the resistivity ratio is obtained by using a preset second formula, wherein the preset first formula is: Where: RSP represents the relative value of natural potential SP, SP max , SP min They represent the natural potential value at any point and the maximum and minimum natural potential of the target layer respectively. The preset second formula is: Where: RR represents the relative value of resistivity, R t , R s , R xo They represent the deep resistivity, shallow resistivity and intrusion zone resistivity of the formation respectively.

9. A natural water-flooded oil layer identification device, characterized in that: It includes a logging response characteristic parameter acquisition module, a first calculation module, a demarcation threshold generation module, a second calculation module, and an identification module, wherein: The logging response characteristic parameter acquisition module is used to obtain the logging response characteristic parameters of the conventional oil layer, the poor oil layer, the natural water-flooded oil layer and the water layer of the coring well of the structural adjustment oil reservoir, and the logging response characteristic parameters at least include the natural potential SP, the deep resistivity Rt, the shallow resistivity Rs, and the intrusion zone resistivity Rxo; The first calculation module is used to calculate the natural potential relative value parameters and resistivity ratios of conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers respectively using the logging response characteristic parameters, wherein the natural potential relative value parameters are used to reflect the differences in natural potentials of conventional oil layers, water-flooded layers and water layers at different well points, and the resistivity ratio parameters are used to reflect the differences in the distribution of resistivity values ​​and the changing laws of the ratios among conventional oil layers, poor oil layers, water-flooded layers and water layers; The demarcation threshold value generating module is used to obtain the demarcation threshold values ​​of the natural potential relative value parameter and the resistivity ratio for conventional oil layers, poor oil layers, natural water-flooded oil layers and water layers by using the intersection distribution of the natural potential relative value parameter and the resistivity ratio; The second calculation module is used to obtain the logging response characteristic parameters of the non-coring well to be identified, and calculate the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified; The identification module is used to match the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified with the demarcation threshold to identify the oil layer, poor oil layer, natural water-flooded oil layer and water layer of the non-coring well.

10. A natural water-flooded oil layer identification device, characterized in that: It includes a calculation module and an identification module, wherein: The calculation module is used to obtain the logging response characteristic parameters of the non-coring well to be identified, and calculate the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified, wherein the logging response characteristic parameters at least include natural potential, deep resistivity, shallow resistivity, and intrusion zone resistivity; The identification module is used to use the natural potential relative value parameters and resistivity ratio of the non-coring well to be identified to match with the preset demarcation threshold value to identify the conventional oil layer, poor oil layer, natural water-flooded oil layer and water layer of the coring well. The preset demarcation threshold value is the natural potential relative value parameters and resistivity ratio that the conventional oil layer, poor oil layer, natural water-flooded oil layer and water layer need to meet simultaneously.

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