Shale oil reservoir measure well selection method

Abstract

The invention discloses a shale oil reservoir measure well selection method, which comprises the following steps of: 1, solving geological factors according to logging parameters; engineering factors are solved according to the liquid adding amount of each well; 2, calculating geological engineering factors according to the geological factors and the engineering factors; according to the production condition of the well, the production cycle is averagely divided into blocks, and the declining rate of the blocks in each cycle is calculated; 3, calculating the theoretical yield according to the initial yield, declining rate and production duration of the well; 4, calculating production factors according to the theoretical yield, the initial yield, the declining rate and the current actual yield; 5, performing two-dimensional image representation according to the production factor and the geological engineering factor; and the two-dimensional image representation is distinguished and judged whether to take measures or not in combination with the yield change rule before and after the measures.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum exploration and development, and in particular to a method for selecting a measure well in a shale oil reservoir. Background Art

[0002] As the exploration of conventional oil resources continues to increase, the difficulty of exploration is increasing. The quality of newly added reserves is poor and the recovery rate is low. At the same time, the developed oil fields have gradually entered the production decline period, and it is difficult to maintain stable production and increase production. Therefore, the oil industry strives to find major replacement resources and leap from conventional oil and gas to unconventional oil and gas. Unconventional oil and gas mainly include shale oil (gas) and tight oil (gas). As one of the unconventional oil and gas resources, tight oil is widely distributed and has huge resource potential. The global technically recoverable reserves are about 639.3×10 8 t, becoming a new hot spot for global unconventional oil and gas exploration and development, and is known as the "black gold" of the oil industry.

[0003] Although unconventional oil and gas exploration started late, it is rich in resources and widely distributed. In recent years, exploration discoveries and breakthroughs have been made in multiple basins, and multiple large-scale production capacity areas have been initially built. By 2022, the proven geological reserves of unconventional oil and gas are 7.37×10 8 t, with a built capacity of 400×10 4 t / a or above.

[0004] Since the physical properties of unconventional oil reservoirs are very poor, it is difficult to exploit them through natural energy. They must be supplemented with energy through volume fracturing to achieve exploitation. Therefore, the production well type commonly used to develop such oil reservoirs is horizontal wells. However, there is no distinction in the selection of well measures. Usually, for wax-containing oil reservoirs, after a period of production, horizontal wells will form wax on the inner wall of the casing and the inner wall of the oil pipe in the vertical well section. The so-called waxing phenomenon refers to the fact that for crude oil with a certain amount of paraffin, during the production process, as the temperature and pressure decrease and the gas precipitates, the dissolved paraffin will precipitate, aggregate and deposit on the surface of the solid phase such as the pipe wall in the form of crystals. For oil reservoirs with high formation water mineralization, during the production process, as the production continues, scale will form on the pipe wall, thus affecting normal production; for unconventional oil reservoirs, due to the fine lithology of the reservoir, sand production is often accompanied during the production process, and sand production will also cause abnormal production. Whether it is wax, scale or sand, most of them will cause the variable load to increase and reduce the service life of the oil rod and oil pipe; at the same time, it will also reduce the cross-section of the oil pipe and cause blockage, increase the outer diameter of the sucker rod, increase the oil flow resistance, and easily lead to oil well blockage, pump jam and pump leakage, etc., affecting the normal production of the oil well, reducing the output of the pumping well, and even causing the oil well to stop production, affecting the effectiveness of the well measures.

[0005] Therefore, based on the above problems, how to judge whether measures should be taken for a well is an issue that we urgently need to face and solve. Summary of the invention

[0006] In view of the problem in the prior art that there is no distinction in the selection of measures for wells, resulting in unsatisfactory measures and waste of production resources, the present invention provides a method for selecting measure wells in shale oil reservoirs, which can quickly judge the quality of the geological conditions of the oil wells and the pros and cons of the engineering factors added by the fracturing project, and effectively improve the accuracy of the selection and judgment of the measure wells.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for selecting a shale oil reservoir measure well, the method comprising the following steps:

[0009] Step 1: Obtain geological factors based on well logging parameters; obtain engineering factors based on the amount of fluid added to each well;

[0010] Step 2: Calculate the geological and engineering factors based on the geological factors and engineering factors; divide the production cycle into blocks evenly based on the production situation of the well, and calculate the decline rate of the blocks in each cycle;

[0011] Step 3: Calculate the theoretical production based on the initial production, decline rate and production time of the well;

[0012] Step 4: Calculate the production factor based on the theoretical output, initial output, decline rate and current actual output;

[0013] Step 5: Make a two-dimensional image representation based on production factors and geological engineering factors; and combine the production change rules before and after the measures to distinguish the two-dimensional image representation and determine whether to take measures.

[0014] Furthermore, the logging parameters include porosity, permeability, saturation after logging interpretation, interpreted thickness of the horizontal section, length of the horizontal section, sum of thickness of Class I and Class II encountered in the horizontal section, and single layer thickness after logging interpretation.

[0015] Furthermore, the geological factor is calculated according to the following formula:

[0016]

[0017] Furthermore, the engineering factor is calculated according to the following formula:

[0018]

[0019] Furthermore, the address engineering factor is calculated according to the following formula:

[0020]

[0021] Furthermore, during the calculation of the block decrease rate, the decrease rate is calculated separately for the time period when the decrease rate is greater than 50%.

[0022] Furthermore, according to the block decrease rate in different periods, the annual block decrease rate is obtained;

[0023] Based on the annual block decline rate and the production time in years, the formula is as follows:

[0024] Current theoretical output = initial output × (1-annual decline rate) 生产年数 ;

[0025] Based on the annual block decline rate and the production time in months, the formula is as follows:

[0026]

[0027] Furthermore, when the annual decline rate of blocks is calculated and the production time is in years, the formula is as follows:

[0028] Production factor = initial output × (1-annual decline rate) 生产年数 - Current actual output |;

[0029] To find the annual block decline rate and the production time is in months, the formula is as follows:

[0030]

[0031] Furthermore, based on the two-dimensional image representation of geo-engineering factors and production factors, the geo-engineering conditions are divided: measures are selected for wells with production factors greater than or equal to 2.0 ± 0.5.

[0032] Compared with the prior art, the present invention has the following beneficial technical effects:

[0033] In order to more clearly judge whether production wells need to be treated, the present invention provides a method for selecting treatment wells in shale oil reservoirs. By calculating the geological factors and engineering factors by logging parameters, the geological conditions of the oil wells and the engineering factors added by the fracturing project can be quickly judged. At the same time, the geological engineering factors and the production cycle are used to judge and consider multiple factors such as the increase in reservoir decline rate, production time and theoretical output, which effectively improves the accuracy of the optimal judgment of treatment wells, provides a strong and effective guarantee for the stable production and increase of unconventional oil reservoirs, and provides technical support for solving practical problems in the development and production of similar oil reservoirs.

[0034] Furthermore, the present invention provides a shale oil reservoir measure well selection method, which combines multiple parameters of the geological reservoir parameters such as the porosity, permeability, saturation and thickness; and considers engineering parameters such as the amount of fracturing fluid added to the formation in the fracturing measure to obtain the geological engineering factor; then takes into account the factor of unconventional oil reservoir decline, obtains the current theoretical output, and the difference between the theoretical output and the actual output, obtains the production factor, and establishes an identification chart of the geological engineering factor and the production factor. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0036] Figure 1 An unconventional reservoir measure well selection diagram for a shale oil reservoir measure well selection method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0038] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0039] When the unconventional oil reservoir resources in an oil field are large, horizontal wells are mainly used for exploitation. However, due to the high wax content, high scale content, and high sand production of regional crude oil, normal production capacity will be affected during the production process. An embodiment of the present invention provides a preferred shale oil reservoir measure well selection method, which is suitable for judging whether measures should be taken after a period of production in an unconventional oil reservoir production well.

[0040] The selection method includes the following steps:

[0041] Step 1: Obtain geological factors.

[0042] The geological factor per meter is calculated based on the porosity, permeability, saturation interpreted by well logging, the single-layer thickness interpreted by well logging, the interpreted thickness of the horizontal section or the length of the horizontal section or the Class I and Class II thickness encountered in the horizontal section.

[0043] The specific formula is as follows:

[0044]

[0045] After a horizontal well is completed, the geological conditions are fixed. Since the geological conditions are positively correlated with porosity, permeability and saturation, that is, the higher the porosity, the better the geological conditions, the higher the permeability, the better the geological conditions, and the higher the saturation, the better the geological conditions, the geological factors of the well can be clearly reflected through porosity, permeability, saturation, single-layer thickness interpreted by logging, horizontal section length or interpreted thickness of the horizontal section or Class I and Class II thickness encountered in the horizontal section.

[0046] Step 2: Obtain the engineering factor.

[0047] For unconventional oil reservoirs, hydraulic fracturing is required after the horizontal well is drilled. The quality of hydraulic fracturing is directly related to the amount of sand and liquid added. The main function of adding sand is to support the formation fractures.

[0048] The optimal amount of fluid added is the main engineering parameter. Generally speaking, the greater the amount of fluid added, the better the fracturing effect, the higher the formation energy replenished, and the better the development effect. Therefore, the engineering factor per meter is calculated based on the amount of fluid added for each well.

[0049] The specific formula is as follows:

[0050]

[0051] Step 3: Obtain the geoengineering factor, referred to as GEF.

[0052] Since the geo-engineering factors are fixed after a well is drilled and fractured, the geo-engineering factors are positively correlated with the geological factors and positively correlated with the engineering factors.

[0053] The specific formula is as follows:

[0054]

[0055] Step 4: Calculate the decreasing rate of the block.

[0056] According to the production situation of old wells, the production cycle is evenly divided into blocks:

[0057] The first method: When the production cycle is long, greater than or equal to two years, the annual decline rate is calculated based on the production of old wells, and the decline rates of all wells are averaged as the annual decline rate of the block.

[0058] For the case where the decline rate in the first year is greater than or equal to 50%, the decline rate of the new well in the first year of production is calculated separately, or the decline rate in the second year, third year, ... nth year, etc. is calculated. It is necessary to average the blocks and then calculate the decline rate of the average block to clearly express the production rules of the blocks in turn.

[0059] The second method: When the production cycle is long, greater than or equal to two months, the monthly decline rate is calculated based on the production of old wells, and the decline rates of all wells are averaged as the monthly decline rate of the block.

[0060] For the case where the decline rate in the first month is greater than or equal to 50%, the decline rate of the new well in one month of production is calculated separately, or the decline rate in the second month, the third month, ... the nth month, etc. is calculated.

[0061] In the actual calculation process summary, it is necessary to average the blocks and then calculate the decreasing rate of the average blocks to clearly express the production law of the blocks.

[0062] Step 5: Calculate the current theoretical production of a single well.

[0063] The current theoretical yield is related to the initial yield, production interval and decline rate.

[0064] When the annual block decline rate is obtained and the production time is in years, the formula is as follows:

[0065] Current theoretical output = initial output × (1-annual decline rate) 生产年数

[0066] To find the annual block decline rate and the production time is in months, the formula is as follows:

[0067]

[0068] Step 6: Obtain the production factor, which can be abbreviated as △P.

[0069] The current theoretical output is related to the initial output, production time and decline rate. When the annual decline rate of the block is obtained and the production time is in years, the formula is as follows:

[0070] Production factor = initial output × (1-annual decline rate) 生产年数 - Current actual production |

[0071] To find the annual block decline rate and the production time is in months, the formula is as follows:

[0072]

[0073] Step 7: Create production factor and geological engineering factor charts.

[0074] The horizontal axis is the geological engineering factor, and the vertical axis is the production factor. An intersection diagram is drawn up and a production factor and geological engineering factor chart is established.

[0075] Step 8: The actual measures data that have taken place, including daily oil increase data before and after the measures, initial production of the measures, production after the measures, production time, horizontal section length, horizontal section drilling interpretation length, the sum of Class I and Class II thickness encountered in the horizontal section, porosity, permeability, saturation, thickness parameters,

[0076] Calculate and obtain geological engineering factors and production factors, and establish production factor and geological engineering factor charts.

[0077] like Figure 1 As shown, according to the change pattern of output before and after the measures, the chart is divided into four types: I, II, III, and IV.

[0078] Category I represents good geological and engineering conditions, large yield gaps, and large room for yield increases after measures are taken;

[0079] Category II represents general geological and engineering conditions, large yield gaps, and large potential for yield increases after measures are taken;

[0080] Class III means that the geological and engineering conditions are good, the yield gap is small, and no further measures are required;

[0081] Category IV means that the geological and engineering conditions are general, the yield gap is small, and no further measures are required.

[0082] The technical solution provided by the present invention establishes a geological engineering factor by considering the geological conditions of the oil well itself and the engineering factors added by the fracturing project; when the well is drilled and fracturing is completed, the geological engineering factor is a fixed value and will not change with the addition of a newly completed well.

[0083] At the same time, the technical solution of the present invention takes into account factors such as reservoir decline rate, production time and theoretical output, establishes production factors, and establishes the gap in theoretical output through production factors, that is, the reference value of the theoretical increment of measures, so that the selection of measures to determine whether unconventional oil reservoir production wells need to be more targeted, while ensuring effectiveness and accuracy.

[0084] Therefore, this technical solution has important practical significance for ensuring the reasonable and normal production operation of unconventional oil reservoirs, and provides a reference for the production and exploitation of unconventional oil reservoirs.

[0085] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0086] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for selecting a shale oil reservoir well, characterized in that: The selection method includes the following steps: Step 1: Obtain geological factors based on well logging parameters; obtain engineering factors based on the amount of fluid added to each well; Step 2: Calculate the geological and engineering factors based on the geological factors and engineering factors; divide the production cycle into blocks evenly based on the production situation of the well, and calculate the decline rate of the blocks in each cycle; Step 3: Calculate the theoretical production based on the initial production, decline rate and production time of the well; Step 4: Calculate the production factor based on the theoretical output, initial output, decline rate and current actual output; Step 5: Make a two-dimensional image representation based on production factors and geological engineering factors; and combine the production change rules before and after the measures to distinguish the two-dimensional image representation and determine whether to take measures.

2. A method for selecting a shale oil reservoir measure well according to claim 1, characterized in that: The logging parameters include the porosity, permeability, saturation after logging interpretation, the interpreted thickness of the horizontal section, the length of the horizontal section, the sum of the thickness of Class I and Class II encountered in the horizontal section, and the single layer thickness after logging interpretation.

3. The method for selecting a shale oil reservoir measure well according to claim 1, characterized in that: The geological factor is calculated according to the following formula:

4. A method for selecting a shale oil reservoir measure well according to claim 1, characterized in that: The engineering factor is calculated according to the following formula:

5. The method for selecting a shale oil reservoir measure well according to claim 1, characterized in that: The address engineering factor is calculated according to the following formula:

6. A method for selecting a shale oil reservoir measure well according to claim 1, characterized in that: During the calculation of the block decrease rate, the decrease rate is calculated separately for the time period when the decrease rate is greater than 50%.

7. The method for selecting a shale oil reservoir measure well according to claim 1, characterized in that: According to the block decrease rate in different periods, the annual block decrease rate is obtained; Based on the annual block decline rate and the production time in years, the formula is as follows: Current theoretical output = initial output × (1-annual decline rate) 生产年数 ; Based on the annual block decline rate and the production time in months, the formula is as follows:

8. The method for selecting a shale oil reservoir measure well according to claim 1, characterized in that: To find the annual block decline rate and the production time is in years, the formula is as follows: Production factor = initial output × (1-annual decline rate) 生产年数 - Current actual output |; To find the annual block decline rate and the production time is in months, the formula is as follows:

9. A method for selecting a shale oil reservoir measure well according to claim 1, characterized in that: Based on the two-dimensional image representation of geo-engineering factors and production factors, the geo-engineering conditions are divided: measures are selected for wells with production factors greater than or equal to 2.0 ± 0.5.

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