A shale gas well plunger drainage gas production analysis method, device and plunger structure

Abstract

The present application provides a kind of shale gas well plunger drainage gas production analysis method, device and plunger structure;The method comprises: obtaining the corresponding relationship of the test well depth and inclination angle of plunger;Corresponding relationship of the falling moment and inclination angle of plunger is obtained;According to the corresponding relationship of the test well depth and inclination angle of plunger and the corresponding relationship of the falling moment and inclination angle of plunger, gas-liquid interface well depth and plunger stop well depth are determined;According to gas-liquid interface well depth and plunger stop well depth, the lifting efficiency of plunger is determined, and the drainage gas production performance of plunger is analyzed.The analysis method provided by the present application can effectively guide the shale gas plunger process well in different production periods, the optimization of downhole limiter and plunger in plunger process technical scheme, the optimization of plunger operation system in production management, and has wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and in particular to a method, apparatus and plunger structure for analyzing plunger drainage gas production in shale gas wells. Background Technology

[0002] In shale gas extraction, the initial rapid production increase mainly relies on the commissioning of a large number of new wells. As extraction time increases, shale gas well production declines rapidly, entering a low-pressure, low-production stage in less than two years, requiring long-term drainage and gas production to maintain capacity. Shale gas wells are characterized by long-term low pressure, low production, and strong storage capacity in long horizontal sections, which makes it easy for production fluid to retreat back to the horizontal section, requiring the drainage and gas production technology to be effective in the long term.

[0003] Extensive technical research and field practice have revealed that the plunger lift process is the preferred technology for late-stage drainage and gas production in shale gas wells. Through targeted technological measures, it is possible to prevent all the fluid accumulated in the wellbore (tubing) from flowing back to the horizontal section, creating a water supply to the plunger to carry the fluid out of the wellhead. This fully utilizes the well's own energy to discharge the accumulated fluid, thus achieving the long-term, economical, and effective drainage requirements.

[0004] Some studies have focused on assessing plunger performance by analyzing parameter changes in field applications. For example, Method 1 compares gas and water production changes before and after the process, with increased production indicating an effective plunger process. Advantages: Direct use of production data, readily available, and simple calculation. Disadvantages: This method uses production as a parameter. Shale gas wells use rotating metering surface processes. A platform typically has six wells and two metering processes: one for accurate real-time metering of one well, and the other for shared metering of the remaining wells. Single-well production is manually divided, making the data highly susceptible to human error and affecting the results. Shale gas well production is influenced by factors such as well productivity recovery (shutdown and repressurization), surface pressure transmission, inter-well pressure interference, and wellbore blockage or unblocking dynamics. Changes in production are not directly related to the effects of the process's technical solutions and operating procedures.

[0005] Method 2: Compare wellhead pressure and pressure drop per unit production before and after the process. Disadvantages: Formation and wellbore conditions differ before and after the process. During process installation, shutting in the well will restore gas well production capacity; after construction and before commissioning, wellbore fluid accumulation is generally removed using strong drainage processes such as gas lift. The wellbore conditions before and after the process differ significantly, making the comparison unscientific.

[0006] Method 3: Judging the effectiveness of the process by whether the plunger can reach the wellhead. This method misrepresents the concepts of "plunger reaching the wellhead" and "plunger effectively draining and producing gas." The plunger reaching the wellhead is a basic requirement for normal process operation, not evidence of process effectiveness.

[0007] Method 4: Determine the effectiveness of the plunger process by observing whether fluid is pushed out of the wellhead before the plunger reaches it. This method involves listening to the airflow and the sound of the plunger reaching the wellhead, observing changes in the separator fluid level, and checking for significant rebound in the wellhead oil pressure to determine whether fluid is being pushed out of the wellhead and the amount of fluid pushed out. The drawback is that for wells without significant fluid being pushed out, it cannot further determine whether the cause is excessive plunger leakage or insufficient fluid on the limiter, and the guidance for optimizing the process or operating procedures is unclear.

[0008] Method 5: By recording the acoustic signal of the plunger descending at the wellhead, the presence of a liquid surface is interpreted from the signal, qualitatively determining whether a liquid column exists above the plunger, and estimating the length of the liquid column based on the plunger's travel time in the liquid phase. However, since it is uncertain whether the plunger will reach the limit switch, the well depth of the liquid surface cannot be determined by recording the time it takes for the plunger to reach the gas-liquid interface.

[0009] Method 6: Integrate measuring tools such as temperature and pressure gauges and coupling sensors into the plunger tool to interpret the existence and length of the liquid column in the tubing. Similar to Method 5, this method cannot accurately determine the liquid level depth or the final position of the plunger's descent through data processing.

[0010] Some technologies use model calculations to determine the efficiency of plunger gas lift fluid discharge. For example, patent document 201810564941.6 discloses a method for calculating the efficiency of plunger gas lift fluid discharge. It calculates the height of the liquid column above the limiter in the tubing by using the shut-in casing oil pressure difference before well opening, and calculates the driving pressure difference at the moment of plunger start-up, the average speed of plunger lifting, and the average leakage flow rate of liquid during the lifting process to obtain the plunger gas lift fluid discharge efficiency. However, this method assumes that the casing fluid level is deep in the limiter well and that the plunger will definitely fall onto the limiter. These assumptions are not suitable for shale gas wells.

[0011] The basic principle of the plunger process is to rely on the solid interface provided by the plunger to prevent slippage of the gas-water two-phase flow in the wellbore, thereby reducing energy loss caused by slippage and improving the efficiency of fluid carrying in the gas well. Therefore, the presence and quantity of liquid above the plunger after shut-in (the length of the liquid column) are prerequisites for the effectiveness of the plunger process. The amount of liquid pushed out of the wellhead by the plunger is an important direct parameter of the plunger drainage efficiency (plunger lifting effect).

[0012] Whether the method for analyzing the plunger lifting effect is reasonable and accurate is directly related to the objectivity and correctness of the analysis results, which will inevitably affect the effectiveness of on-site technical policies, and thus affect the cost and benefits of shale gas well development.

[0013] The key parameters for the efficiency of plunger lifting with fluid are the liquid column above the plunger and the leakage during operation. The measurement and calculation methods of these parameters are crucial to the analysis of the plunger lifting effect, but there is currently no good practical solution.

[0014] Recent research on intelligent plungers has yielded mature temperature and pressure measuring plunger products. These products integrate measuring tools such as temperature and pressure gauges into the plunger, recording temperature and pressure parameters at different times as the plunger falls and rises in the wellbore. However, the measured temperature and pressure data cannot be accurately correlated with well depth and cannot be used for wellbore flow profile analysis.

[0015] While there are many existing methods for analyzing the effects of plunger processes, most are qualitative or indirect analyses, lacking the ability to conduct direct and objective quantitative analyses. This limits their effectiveness in accurately selecting optimal process technologies and optimizing production operation systems. Summary of the Invention

[0016] This invention determines parameters such as the well depth of the gas-liquid interface within the tubing, the stop position of the plunger during descent, and the amount of liquid pushed out of the wellhead by the plunger, without increasing construction costs. This provides direct quantitative data and a standardized methodology for analyzing the plunger lift effect in shale gas wells. This invention also provides a method, apparatus, and system for analyzing plunger drainage gas production in shale gas wells, specifically for analyzing the performance of downhole limiters and plungers in shale gas plunger wells and their lift effect under dynamic and static conditions.

[0017] To achieve the above objectives, the technical solution of the present invention is as follows:

[0018] A method for analyzing plunger drainage gas production in shale gas wells, the method comprising:

[0019] Obtain the correspondence between the test well depth and the well inclination angle of the plunger;

[0020] Obtain the correspondence between the plunger's descent time and the well inclination angle;

[0021] Based on the correspondence between the test well depth and the well inclination angle of the plunger and the correspondence between the plunger's descent time and the well inclination angle, the gas-liquid interface well depth and the plunger stopping well depth are determined.

[0022] Based on the gas-liquid interface depth and the plunger stopping depth, the plunger's liquid lifting efficiency is determined, and the plunger's drainage gas production performance is analyzed.

[0023] Furthermore, the gas-liquid interface well depth is determined based on the test well depth determined by the well inclination angle, the plunger's descent velocity, and the plunger's descent time corresponding to the well inclination angle.

[0024] The plunger's descent speed is determined based on the test well depth corresponding to the well inclination angle and the descent time corresponding to the well inclination angle.

[0025] Furthermore, the determination of the gas-liquid interface well depth specifically includes,

[0026]

[0027] Where k is the interval between plunger recording times, and n+1, n+2, and n+3 are the sequence numbers of the plunger records, with n+2 corresponding to the first plunger record entering the liquid; D g-w D represents the depth of the gas-liquid interface well. n+1 and D n+2 These are the well depths corresponding to serial numbers n+1 and n+2, respectively; v n+1 and v n+3 These are the falling speeds of the plungers corresponding to serial numbers n+1 and n+3, respectively.

[0028] Furthermore, the process for determining the gas-liquid interface well depth specifically includes:

[0029] Obtain the one-to-one correspondence between well inclination angle, fall time, and test well depth;

[0030] The plunger descent speed is determined based on the test well depth corresponding to the well inclination angle and the descent time corresponding to the well inclination angle.

[0031] Serial Number Falling time t Well inclination angle Φ Test well depth D plunger falling speed v 1 0 0 0 0 … … … … … n <![CDATA[t n ]]> <![CDATA[Φ n ]]> <![CDATA[D n ]]> <![CDATA[v n =(D n -D n-k ) / (t n -t n-k )]]> n+1 <![CDATA[t n+k ]]> <![CDATA[Φ n+1 ]]> <![CDATA[D n+1 ]]> <![CDATA[v n+1 =(D n+1 -D n ) / (t n+k -t n )]]> n+2 <![CDATA[t n+2k ]]> <![CDATA[Φ n+2 ]]> <![CDATA[D n+2 ]]> <![CDATA[v n+2 =(D n+2 -D n+1 ) / (t n+2k -t n+k )]]> n+3 <![CDATA[t n+3k ]]> <![CDATA[Φ n+3 ]]> <![CDATA[D n+3 ]]> <![CDATA[v n+3 =(D n+3 -D n+2 ) / (t n+3k -t n+2k )]]> … … … … … X <![CDATA[t X ]]> <![CDATA[Φ X ]]> <![CDATA[D X ]]> 0

[0032] Wherein, the sequence number is a consecutive integer, taking the values ​​1, 2, 3, ..., n, n+1, n+2, n+3, ..., X, where n+2 corresponds to the first sequence number recorded by the plunger entering the liquid, X is the sequence number in which the plunger stops; k is the time interval;

[0033] Gas-liquid interface depth D g-w Located in D n+2 and D n+1 between,

[0034] D g-w =D n+1 +h g

[0035] h g For t n+k and t n+2k The length of the air column during the piston's movement within a given time period;

[0036] h g +h w =D n+2 -D n+1

[0037] h w For t n+k and t n+2k The length of the liquid column during the plunger's movement at a given time;

[0038] t g +t w =k

[0039] t g and tw t n+k and t n+2k Within a given time interval, the time the plunger spends moving in the gas column and the time the plunger spends moving in the liquid column;

[0040] t n+k and t n+2k At time t, the plunger's velocity in the air column is v. n+1 The plunger's velocity in the liquid column is v n+3 ;

[0041] h g =v n+1 ×t g

[0042] h w =v n+3 ×t w

[0043]

[0044]

[0045] Furthermore, the determination of the plunger's liquid lifting efficiency is as follows:

[0046] The lifting efficiency of the plunger is determined based on the volume of liquid lifted by the plunger and the volume of the liquid column above the plunger.

[0047] The volume of the liquid column above the plunger is determined based on the gas-liquid interface depth and the plunger stopping depth.

[0048] The volume of liquid lifted by the plunger is determined based on the liquid collected in the separator.

[0049] Furthermore, determining the specific liquid lifting efficiency of the plunger includes,

[0050] Determine the volume of the liquid column above the plunger:

[0051]

[0052] L wpu =D p -D g-w

[0053] Where V0 is the volume of the liquid column at the top of the plunger, and d t L is the inner diameter of the oil pipe. wpu D is the length of the liquid column above the plunger. p D represents the well depth at which the plunger stops inside the tubing. g-w The depth of the gas-liquid interface;

[0054] The volume of liquid lifted by the plunger is determined to be [value missing].

[0055]

[0056] Where V1 is the volume of liquid lifted by the plunger, and d se Let be the inner diameter of the separator, and h be the height of the newly added liquid level in the separator; determine the liquid lifting efficiency of the plunger as .

[0057]

[0058] Where η is the liquid lifting efficiency of the plunger, V1 is the volume of liquid lifted by the plunger, and V0 is the volume of the liquid column above the plunger.

[0059] Furthermore, the method also includes analyzing the performance of the limiter, specifically including,

[0060] Determine the length of the liquid column above the limiter based on the gas-liquid interface depth and the limiter depth:

[0061] L wsu =D st -D g-w ;

[0062] Among them, L wsu D is the length of the liquid column above the limiter. st For the limiter well depth, D g-w The depth of the gas-liquid interface;

[0063] The well depth of the limiter is determined based on the correspondence between the test well depth of the plunger and the well inclination angle.

[0064] Another aspect of the present invention provides a shale gas well plunger drainage gas production analysis device, the device comprising:

[0065] The acquisition unit is used to acquire the correspondence between the test well depth and the well inclination angle of the plunger, and the correspondence between the plunger's descent time and the well inclination angle.

[0066] The determination unit is used to determine the gas-liquid interface depth, the plunger stopping depth, and the limiter depth based on the correspondence between the plunger's test well depth and the well inclination angle, and the correspondence between the plunger's descent time and the well inclination angle.

[0067] The analysis unit is used to determine the liquid lifting efficiency of the plunger based on the gas-liquid interface depth and the plunger stopping depth, and to analyze the plunger drainage gas production performance.

[0068] Furthermore, the process of determining the gas-liquid interface well depth by the determining unit specifically includes,

[0069] Obtain the one-to-one correspondence between well inclination angle, fall time, and test well depth;

[0070] The plunger descent speed is determined based on the test well depth corresponding to the well inclination angle and the descent time corresponding to the well inclination angle.

[0071]

[0072]

[0073] Wherein, the sequence number is a consecutive integer, taking the values ​​1, 2, 3, ..., n, n+1, n+2, n+3, ..., X, where n+2 corresponds to the first sequence number recorded by the plunger entering the liquid, X is the sequence number in which the plunger stops; k is the time interval;

[0074] Gas-liquid interface depth D g-w Located in D n+2 and D n+1 between,

[0075] D g-w =D n+1 +h g

[0076] h g For t n+k and t n+2k The length of the air column during the piston's movement within a given time period;

[0077] h g +h w =D n+2 -D n+1

[0078] h w For t n+k and t n+2k The length of the liquid column during the plunger's movement at a given time;

[0079] t g +t w =k

[0080] t g and t w t n+k and t n+2k Within a given time interval, the time the plunger spends moving in the gas column and the time the plunger spends moving in the liquid column;

[0081] t n+k and t n+2k At time t, the plunger's velocity in the air column is v. n+1 The plunger's velocity in the liquid column is v n+3 ;

[0082] h g =v n+1 ×t g

[0083] h w =v n+3 ×t w

[0084]

[0085]

[0086] Furthermore, the analysis unit determines the plunger's liquid lifting efficiency specifically by including:

[0087] Determine the volume of the liquid column at the top of the plunger:

[0088]

[0089] L wpu =D p -D g-w

[0090] Where V0 is the volume of the liquid column at the top of the plunger, and d t L is the inner diameter of the oil pipe. wpu D is the length of the liquid column above the plunger. p D represents the well depth at which the plunger stops inside the tubing. g-w The depth of the gas-liquid interface;

[0091] Determine the volume of liquid lifted by the plunger.

[0092]

[0093] Where V1 is the volume of liquid lifted by the plunger, and d se Let be the inner diameter of the separator, and h be the height of the newly added liquid level in the separator; determine the liquid lifting efficiency of the plunger.

[0094]

[0095] Where η is the liquid lifting efficiency of the plunger, V1 is the volume of liquid lifted by the plunger, and V0 is the volume of the liquid column above the plunger.

[0096] Furthermore, the analysis unit is also used to analyze the performance of the limiter, specifically including,

[0097] Determine the length of the liquid column above the limiter based on the gas-liquid interface depth and the limiter depth:

[0098] Among them, L wsu D is the length of the liquid column above the limiter. st For the limiter well depth, D g-w The depth of the gas-liquid interface;

[0099] The well depth of the limiter is determined based on the correspondence between the test well depth of the plunger and the well inclination angle determined by the determining unit.

[0100] This invention also provides a plunger structure for shale gas well drainage and gas production analysis, characterized in that it includes a plunger, a first buffer spring, a well inclination tester, a second buffer spring, and a fixing block.

[0101] The plunger has a hollow structure, and the well inclination tester is disposed inside the hollow structure of the plunger. One end of the well inclination tester is connected to the upper part of the plunger through a first buffer spring, and the other end is connected to a fixed block through a second buffer spring. This invention also provides a plunger structure for shale gas well plunger drainage and gas production analysis, characterized in that it includes a plunger, a first buffer spring, a well inclination tester, a second buffer spring, and a fixed block.

[0102] The plunger has a hollow structure, and the well inclination tester is set inside the hollow structure of the plunger. One end of the well inclination tester is connected to the upper part of the plunger through a first buffer spring, and the other end is connected to the fixed block through a second buffer spring.

[0103] The well inclination tester is used to perform the above-mentioned shale gas well plunger drainage gas production analysis method.

[0104] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0105] 1. This invention is based on the principle that there is a one-to-one correspondence between the inclination angle and depth in the shale gas well build-up section. The relationship between the inclination angle and well depth is derived through the wireline-lowered plunger operation. Furthermore, when the plunger descends from the tubing into the liquid accumulation from the natural gas, its descent velocity drops significantly. By recording the time-inclination angle relationship during the plunger's descent and combining it with measured well depth-inclination angle data, the velocity profile of the plunger in the deviated section can be calculated. This allows for the analysis and calculation of the gas-liquid interface depth, and the determination of the liquid column lengths above the limiter and the plunger, thus assessing the performance of the limiter and the plunger. The overall design of this invention is simple and practical, and it is suitable for analyzing the plunger drainage and gas production effects in shale gas wells.

[0106] 2. This invention can effectively guide the selection of key tools (downhole limiters, plungers) and the optimization of key parameters (plunger operating procedures) in the plunger process technology scheme for shale gas wells at different production stages. It provides an effective analytical method for the efficient development of shale gas and has broad application prospects. Attached Figure Description

[0107] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0108] Figure 1This is a schematic diagram of a shale gas well plunger drainage and gas production plunger structure in a preferred embodiment of the present invention;

[0109] Figure 2 This is a flowchart of the shale gas well plunger drainage gas production analysis method in an embodiment of the present invention;

[0110] Figure 3 This is a spatiotemporal diagram illustrating the movement of the plunger in the oil pipe in an embodiment of the present invention.

[0111] Figure 4 This refers to the relationship between the well inclination angle and the test well depth as determined in this embodiment of the invention.

[0112] Figure 5 This refers to the relationship between the well inclination angle and the plunger descent time as determined in this embodiment of the invention.

[0113] Figure 6 This is a curve showing the relationship between the plunger drop velocity, well inclination angle, and test well depth in an embodiment of the present invention.

[0114] Figure 7 This is a schematic diagram of a shale gas well plunger drainage gas extraction and analysis device in an embodiment of the present invention.

[0115] Explanation of reference numerals in the attached figures:

[0116] 1. Plunger; 2. Well inclination tester; 3-1. First buffer spring; 3-2. Second buffer spring; 4. Fixing block. Detailed Implementation

[0117] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0118] In some embodiments of the present invention, a shale gas well plunger drainage and gas production plunger structure is provided. The plunger structure includes a plunger and a well inclination tester, the plunger and the well inclination tester being connected by a buffer spring. Furthermore, in some preferred embodiments, to better protect the well inclination tester and reduce friction and impact between the well inclination tester and the tubing and limiters, the well inclination tester is installed inside the plunger, and the well inclination tester and the plunger are connected by a buffer spring. In the embodiments of the present invention, there are no strict requirements for the external structure of the plunger; it can be selected according to the properties of the tubing inner wall.

[0119] In a preferred embodiment of the present invention, a schematic diagram of the plunger structure for shale gas well plunger drainage gas production analysis is shown below. Figure 1As shown, the system includes a plunger 1, a first buffer spring 3-1, a well inclination tester 2, a second buffer spring 3-2, and a fixing block 4. The plunger 1 is rod-shaped with serrated grooves on its outer surface. The plunger 1 has a hollow structure. The well inclination tester 2 is installed in the hollow structure of the plunger 1. One end of the well inclination tester 2 is connected to the upper end of the plunger 1 through the first buffer spring, and the other end is connected to the fixing block 4 through the buffer spring.

[0120] The principle of the shale gas well plunger drainage gas production analysis method in this embodiment of the invention is as follows: The plunger falls through several different stages in the tubing. In the gas above the liquid surface in the tubing, the plunger falls at a relatively high speed. After reaching the gas-liquid interface, the plunger's speed drops rapidly under the impact force. The plunger continues to fall at a low speed in the liquid until it stops. The change in speed during this process can be used to determine the medium at the plunger's descent location. Furthermore, in the shale gas well build-up section, the inclination angle and depth have a one-to-one correspondence. This relationship can be obtained by lowering the plunger. Therefore, by recording the relationship between the plunger's descent time and the inclination angle in the tubing, and combining this with the inclination angle and depth recorded by the well inclination tester, the speed during the plunger's descent can be calculated, further determining the gas-liquid interface depth, and thus judging the plunger's liquid lifting efficiency and the performance of the limiter.

[0121] In another embodiment of the present invention, a method for analyzing plunger drainage gas production in shale gas wells is provided, the flowchart of which is shown below. Figure 2 As shown, the method includes:

[0122] Under wireline operation, the plunger is lowered to the limiter of the shale gas well, and the corresponding relationship between the test well depth and well inclination angle when the plunger is lowered is recorded.

[0123] The plunger was deployed into the shale gas well, and the relationship between the plunger's descent time in the tubing and the well inclination angle was recorded.

[0124] Based on the correspondence between the test well depth and the well inclination angle and the relationship between the descent time and the well inclination angle, a one-to-one correspondence between the well inclination angle, well depth, and time is obtained. The plunger descent speed is determined based on the test well depth and the descent time, and the relationship is shown in Table 1.

[0125] Table 1. Correspondence between well inclination angle, well depth, and time, and plunger descent velocity.

[0126] Serial Number Falling time t Well inclination angle Φ Test well depth D plunger falling speed v 1 0 0 0 0 … … … … … n <![CDATA[t n ]]> <![CDATA[Φ n ]]> <![CDATA[D n ]]> <![CDATA[v n =(D n -D n-k ) / (t n -t n-k )]]> n+1 <![CDATA[t n+k ]]> <![CDATA[Φ n+1 ]]> <![CDATA[D n+1 ]]> <![CDATA[v n+1 =(D n+1 -D n ) / (t n+k -t n )]]> n+2 <![CDATA[t n+2k ]]> <![CDATA[Φ n+2 ]]> <![CDATA[D n+2 ]]> <![CDATA[v n+2 =(D n+2 -D n+1 ) / (t n+2k -t n+k )]]> n+3 <![CDATA[t n+3k ]]> <![CDATA[Φ n+3 ]]> <![CDATA[D n+3 ]]> <![CDATA[v n+3 =(D n+3 -D n+2 ) / (t n+3k -t n+2k )]]> … … … … … X <![CDATA[t X ]]> <![CDATA[Φ X ]]> <![CDATA[D X ]]> 0

[0127] Wherein, the sequence number is a consecutive integer, taking the values ​​1, 2, 3, ..., n, n+1, n+2, n+3, ..., X, where n+2 is the sequence number of the plunger entering the liquid surface; k is the interval of the plunger test time; the plunger's falling time, well inclination angle, and test well depth are in a one-to-one correspondence, and the velocity corresponding to a certain test well depth is the test well depth to which the plunger falls within the interval time.

[0128] Combining the data relationships in Table 1 and Figure 3 The diagram showing the spatiotemporal relationship of the plunger movement within the tubing is used to determine the gas-liquid interface depth in the well. From... Figure 3 It can be seen that:

[0129] Gas-liquid interface depth D g-w Located in D n+2 and D n+1 between,

[0130] D g-w =D n+1 +h g

[0131] h g For t n+k and t n+2k The length of the air column during the piston's movement within a given time period;

[0132] h g +h w =D n+2 -D n+1

[0133] h w For t n+k and t n+2k The length of the liquid column during the plunger's movement at a given time;

[0134] t g +t w =k

[0135] t g and t w t n+k and t n+2k Within a given time interval, the time the plunger spends moving in the gas column and the time the plunger spends moving in the liquid column.

[0136] The inventors learned through extensive production practice that after the plunger falls and contacts the liquid surface, due to the confined space inside the oil pipe and the large impact force, the plunger's speed immediately drops significantly and approaches uniformity. However, it will still experience slight variations due to the environmental conditions inside the oil pipe, which affects the moment of entry into the liquid surface. n+2 The velocity calculation has a large error; the velocity v at the moment before entering the liquid surface can be used instead. n+1 and the velocity v at the next moment after entering the liquid surface n+3Calculate the gas-liquid interface depth. At this point, the determined gas-liquid interface depth has good reproducibility with the actual measured value.

[0137] Therefore, in the embodiments of the present invention, t n+k and t n+2k At time t, the plunger's velocity in the air column is v. n+1 The plunger's velocity in the liquid column is v n+3 ;

[0138] h g =v n+1 ×t g

[0139] h w =v n+3 ×t w

[0140] It can be concluded that

[0141] Furthermore,

[0142] Calculate the volume of the liquid column above the plunger and the volume of liquid lifted by the plunger based on the gas-liquid interface depth, and then calculate the plunger's lifting efficiency:

[0143] The volume of the liquid column above the plunger is calculated as follows:

[0144]

[0145] L wpu =D p -D g-w ,

[0146] Where V0 is the volume of the liquid column at the top of the plunger, and d t L is the inner diameter of the oil pipe. wpu D is the length of the liquid column above the plunger. p D represents the well depth at which the plunger stops inside the tubing. g-w The depth of the gas-liquid interface;

[0147] The volume of liquid lifted by the plunger is calculated as follows:

[0148]

[0149] Where V1 is the volume of liquid lifted by the plunger, and d se Where is the inner diameter of the separator, and h is the newly added liquid level height in the separator;

[0150] The plunger's liquid lifting efficiency is...

[0151]

[0152] Where η is the liquid lifting efficiency of the plunger, V1 is the volume of liquid lifted by the plunger, and V0 is the volume of the liquid column above the plunger.

[0153] The higher the lifting efficiency, the more suitable the plunger structure is for the current well conditions and the more reasonable the well opening conditions.

[0154] Calculate the length of the liquid column above the limiter in the tubing based on the gas-liquid interface depth, and analyze the performance of the limiter:

[0155] L wsu =D st -D g-w ;

[0156] Among them, L wsu D is the length of the liquid column above the limiter in the tubing. st D represents the well depth of the tubing limiter. g-w The depth of the well at the gas-liquid interface.

[0157] In the directional drilling section of a shale gas well, there is a one-to-one correspondence between the inclination angle and the depth. As the plunger falls freely through the tubing, its descent speed decreases by orders of magnitude when it enters the liquid phase from the natural gas. Based on the inclination angle corresponding to the moment of abrupt change in the plunger's descent speed, the depth of the gas-liquid interface within the tubing can be determined. Based on the inclination angle at which the plunger stops falling, it can be determined whether the plunger has reached the limit switch and the final depth to which the plunger remains, thus allowing the calculation of the length of the liquid column above the plunger. The plunger can be machined into a hollow structure, and a wellbore inclination measuring instrument can be installed inside. The inclination angle of the plunger can be recorded at unit time steps. By exchanging the inclination angle and depth data recorded by the wellbore inclination measuring instrument in the deviated section, the descent speed of the plunger can be calculated.

[0158] The performance of the limiter and the rationality of the shut-in timing can be evaluated by comparing the height of the liquid column above the limiter. The height of the liquid column in the wellbore is determined by two main factors: first, the amount of liquid accumulated in the tubing from the limiter to the wellhead. This factor is related to the shut-in timing. Shutting in too early helps to preserve the gas well's energy and facilitates the plunger's smooth arrival at the wellhead in the next cycle, but the follow-through production time is short, the gas well's production capacity is insufficient, and the amount of liquid accumulated in the tubing is less, resulting in less liquid carried over in the next cycle; second, the pressure-regulating and flow-cutting performance of the limiter, that is, the limiter's ability to prevent the liquid accumulated in the tubing from retreating to the horizontal section and to open the pressure-regulating valve to release the liquid column when the expected liquid column height is exceeded.

[0159] The shale gas well plunger drainage gas production analysis method according to the embodiments of the present invention is applied to the actual operation of a shale gas well. It should be noted that, based on the movement mode of the plunger in the tubing, the plunger movement in the vertical well section with minimal changes in well inclination angle (from well depth 0 to 2300m in this embodiment) is not representative. Therefore, all data here are statistically analyzed starting from a well depth of 2300m. The specific results are as follows:

[0160] Figure 4 This study records the relationship between the well inclination angle and the test well depth during wireline drilling, where the plunger is lowered to the well depth position relative to the limit switch. Generally, the well inclination angle increases with the test well depth. It is noteworthy that there is a one-to-one correspondence between the well inclination angle and the test well depth. By establishing this relationship, the test well depth can be determined by recording the well inclination angle as the plunger moves through the tubing during plunger drilling.

[0161] Figure 5 This represents the relationship between the wellbore inclination angle and the time of plunger descent after the plunger has reached a depth of 2300m during downhole operation. It can be seen that as time increases, the plunger continues to descend, and the wellbore inclination angle gradually increases until the plunger stops in the fluid, at which point the wellbore inclination angle no longer changes. Clearly, Figure 4 and Figure 5 The inclination angles at the final points are not equal. Figure 4 For 57.83° Figure 5 The angle is 56.54°. This result is because the point where the plunger stops in the tubing is not at the well depth of the limit switch; that is, the plunger did not fall to the limit switch position. This indicates that the method of this embodiment differs from the existing methods of determining the plunger's position and simulating the plunger's movement to the limit switch position. Furthermore, the technical solution in this embodiment is very intuitive. Before applying the plunger for well shut-in operations, the relationship between the well inclination angle and well depth is determined by testing the plunger with a well inclination tester. Subsequently, during the actual application of the plunger in-well operation, the relationship between the well inclination angle and time is recorded, thus determining the relationship between the plunger's movement and the well inclination angle.

[0162] Figure 6 To illustrate the relationship between plunger descent velocity, well inclination angle, and test well depth, the graph shows the relationship between recorded well inclination angle and test well depth, as well as the relationship between recorded well inclination angle and time. Curve a in the figure represents the change in test well depth with well inclination angle; curve b represents the relationship between plunger descent velocity, well inclination angle, and test well depth. It can be seen that the plunger descent velocity is not stable and exhibits certain fluctuations, possibly due to the complex movement of the plunger within the tubing and the friction with the tubing. Furthermore, two distinct points in the plunger descent velocity are clearly visible, corresponding to points X and Y in the graph. From a well depth of 2300m to point X, the plunger moves above the gas-liquid interface. From point X onwards, the plunger moves into the liquid, and the velocity drops sharply; until point Y, the plunger is completely submerged in the liquid, and the plunger velocity stabilizes until it stops in the liquid. Figure 6 The height of the gas-liquid interface can be calculated from the relationship between the plunger's descent speed, the well inclination angle, and the test well depth. The height of the liquid column above the plunger and the height of the limiter can be obtained based on the calculation formula provided in the embodiments of the present invention. After the plunger moves upward, the efficiency of the limiter can be calculated from the liquid discharged to the separator. The results of these calculations, tubing parameters, and separator dimensions are shown in Table 2.

[0163] Table 2. Parameters and calculation results applied to plunger drainage gas production in a shale gas well.

[0164] Gas-liquid interface well depth (m) 2468.4 Piston stopping depth (m) 2549.2 Limiter well depth (m) 2554 Length of the liquid column at the top of the plunger (m) 80.8 Oil pipe inner diameter (mm) 50.67 <![CDATA[Inner area of the oil pipe (m 2 )]]> 0.0020 Volume of liquid column at the top of the plunger (L) 162.85 Separator inner diameter (mm) 576 <![CDATA[Separator area (m 2 )]]> 0.26 Additional liquid level height (mm) in the separator 385 Volume of liquid lifted by the plunger (L) 100.27 Plunger lifting efficiency (%) 61.57

[0165] As can be seen from the results in Table 1, the shale gas plunger drainage gas production method of the present invention can intuitively calculate the well depth of the gas-liquid interface in the tubing, thereby calculating the length of the liquid column above the limiter and the length of the liquid column above the plunger, and further calculating the liquid lifting efficiency of the plunger to analyze the plunger performance.

[0166] It's worth mentioning that currently, global research on wellbore flow primarily involves observing and studying process parameters and phenomena by constructing various inclined or curved pipe devices on the surface that can change diameter and angle. Measurements are recorded and analyzed by altering fluid flow rates and the inclination angle of the inclined pipe. For determining the stable fluid level depth within the tubing, there are generally two methods. One is wireline drilling, where a thermo-barometer is lowered to test the pressure distribution in the wellbore. The fluid level position is then calculated based on the different pressure gradients in the gas and liquid. However, wireline drilling requires a lengthy installation and lowering process, and each test point needs to remain stationary for a certain period, taking several hours in total. Furthermore, the fluid level changes during the pressure recovery process after well shut-in, making this method unsuitable for downhole operations with plungers. The other method uses an echo sounder to calculate the fluid level depth based on the reflection time of sound waves. However, this method's error depends on the sound wave velocity, which varies significantly in the wellbore with changes in pressure, temperature, and even the relative density of the gas, resulting in a large error and making it unsuitable for determining the depth at the gas-liquid interface. To analyze the gas-liquid interface and the depth at which the plunger stops during its descent from the wellhead, one method used in the field involves recording the acoustic waves during the plunger's descent and analyzing the peak values ​​of the acoustic waves caused by vibrations as the plunger passes through tubing couplings. The depth at which the plunger reaches the fluid surface is then calculated based on the tubing length. However, this method has limitations. The peak phenomena are not obvious when the plunger passes through certain couplings, and the acoustic waves attenuate significantly after the plunger enters the water, making it difficult to determine the depth at which the plunger stops.

[0167] In summary, the analysis method provided in this invention allows for a direct analysis of the performance of the plunger and downhole limiter based on the correspondence between well inclination angle and well depth, and between well inclination angle and plunger descent time, according to the plunger's motion changes within the tubing. Furthermore, the method in this invention does not impose strict requirements on the plunger structure, allowing for the selection of appropriate plungers based on the tubing's properties, thus achieving efficient and reliable analysis.

[0168] An embodiment of the present invention also provides a shale gas well plunger drainage gas production analysis device for performing the above-described analysis method, and a schematic diagram of the shale gas well plunger drainage gas production analysis device is shown below. Figure 7 As shown, it includes:

[0169] The acquisition unit is used to acquire the correspondence between the test well depth and the well inclination angle of the plunger, and the correspondence between the plunger's descent time and the well inclination angle.

[0170] The determination unit is used to determine the gas-liquid interface depth, the plunger stopping depth, and the limiter depth based on the correspondence between the plunger's test well depth and the well inclination angle, and the correspondence between the plunger's descent time and the well inclination angle.

[0171] The analysis unit is used to determine the liquid lifting efficiency of the plunger based on the gas-liquid interface depth and the plunger stopping depth, and to analyze the plunger drainage gas production performance.

[0172] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for analyzing plunger drainage gas production in shale gas wells, characterized in that, The method includes: Obtain the correspondence between the test well depth and the well inclination angle of the plunger; Obtain the correspondence between the plunger's descent time and the well inclination angle; Based on the correspondence between the test well depth and the well inclination angle of the plunger and the correspondence between the plunger's descent time and the well inclination angle, the gas-liquid interface well depth and the plunger stopping well depth are determined. Based on the gas-liquid interface depth and the plunger stopping depth, the plunger's liquid lifting efficiency is determined, and the plunger drainage gas production performance is analyzed. The gas-liquid interface well depth is determined based on the test well depth determined by the well inclination angle, the plunger's descent velocity, and the plunger's descent time corresponding to the well inclination angle. The plunger's descent speed is determined based on the test well depth corresponding to the well inclination angle and the plunger's descent time corresponding to the well inclination angle; The determination of the gas-liquid interface well depth specifically includes... Where k is the interval between plunger recording times, and n+1, n+2, and n+3 are the sequence numbers of the plunger records, with n+2 corresponding to the first plunger record entering the liquid; D g-w D represents the depth of the gas-liquid interface well. n+1 and D n+2 These are the well depths corresponding to serial numbers n+1 and n+2, respectively; v n+1 and v n+3 These are the falling speeds of the plungers corresponding to serial numbers n+1 and n+3, respectively. The liquid lifting efficiency of the plunger is determined as follows: The lifting efficiency of the plunger is determined based on the volume of liquid lifted by the plunger and the volume of the liquid column above the plunger. The volume of the liquid column above the plunger is determined based on the gas-liquid interface depth and the plunger stopping depth. The volume of liquid lifted by the plunger is determined based on the liquid collected in the separator.

2. The method according to claim 1, characterized in that, Determining the plunger's liquid lifting efficiency specifically includes, Determine the volume of the liquid column above the plunger: L wpu =D p -D g-w Where V0 is the volume of the liquid column at the top of the plunger, and d t L is the inner diameter of the oil pipe. wpu D is the length of the liquid column above the plunger. p D represents the well depth at which the plunger stops inside the tubing. g-w The depth of the gas-liquid interface; The volume of liquid lifted by the plunger is determined to be [value missing]. Where V1 is the volume of liquid lifted by the plunger, and d se Where is the inner diameter of the separator, and h is the newly added liquid level height in the separator; The pumping efficiency of the plunger is determined to be [value missing]. in, V1 represents the liquid lifting efficiency of the plunger, V0 represents the volume of liquid lifted by the plunger, and V0 represents the volume of the liquid column above the plunger.

3. The method according to claim 1, characterized in that, The method also includes analyzing the performance of the limiter, specifically including, Determine the length of the liquid column above the limiter based on the gas-liquid interface depth and the limiter depth: L wsu =D st -D g-w ; Among them, L wsu D is the length of the liquid column above the limiter. st For the limiter well depth, D g-w The depth of the gas-liquid interface; The well depth of the limiter is determined based on the correspondence between the test well depth of the plunger and the well inclination angle.

4. A shale gas well plunger drainage gas production and analysis device, characterized in that, The device includes: The acquisition unit is used to acquire the correspondence between the test well depth and the well inclination angle of the plunger, and the correspondence between the plunger's descent time and the well inclination angle. The determination unit is used to determine the gas-liquid interface depth, the plunger stopping depth, and the limiter depth based on the correspondence between the plunger's test well depth and the well inclination angle, and the correspondence between the plunger's descent time and the well inclination angle. The analysis unit is used to determine the liquid lifting efficiency of the plunger based on the gas-liquid interface depth and the plunger stopping depth, and to analyze the plunger drainage gas production performance. The gas-liquid interface well depth is determined based on the test well depth determined by the well inclination angle, the plunger's descent velocity, and the plunger's descent time corresponding to the well inclination angle. The plunger's descent speed is determined based on the test well depth corresponding to the well inclination angle and the plunger's descent time corresponding to the well inclination angle; The determination of the gas-liquid interface well depth specifically includes... Where k is the interval between plunger recording times, n+1, n+2, and n+3 are the plunger recording numbers, where n+2 corresponds to the first plunger entry into the liquid; Dg-w is the gas-liquid interface well depth, Dn+1 and Dn+2 are the well depths corresponding to numbers n+1 and n+2, respectively; vn+1 and vn+3 are the plunger descent velocities corresponding to numbers n+1 and n+3, respectively. The liquid lifting efficiency of the plunger is determined as follows: The lifting efficiency of the plunger is determined based on the volume of liquid lifted by the plunger and the volume of the liquid column above the plunger. The volume of the liquid column above the plunger is determined based on the gas-liquid interface depth and the plunger stopping depth. The volume of liquid lifted by the plunger is determined based on the liquid collected in the separator.

5. The apparatus according to claim 4, characterized in that, The analysis unit determines the plunger's liquid lifting efficiency specifically by including, Determine the volume of the liquid column at the top of the plunger: L wpu =D p -D g-w Where V0 is the volume of the liquid column at the top of the plunger, and d t L is the inner diameter of the oil pipe. wpu D is the length of the liquid column above the plunger. p D represents the well depth at which the plunger stops inside the tubing. g-w The depth of the gas-liquid interface; Determine the volume of liquid lifted by the plunger. Where V1 is the volume of liquid lifted by the plunger, and d se Where is the inner diameter of the separator, and h is the newly added liquid level height in the separator; Determine the plunger's liquid lifting efficiency. in, V1 represents the liquid lifting efficiency of the plunger, V0 represents the volume of liquid lifted by the plunger, and V0 represents the volume of the liquid column above the plunger.

6. The apparatus according to claim 4, characterized in that, The analysis unit is also used to analyze the performance of the limiter, specifically including... Determine the length of the liquid column above the limiter based on the gas-liquid interface depth and the limiter depth: Among them, L wsu D is the length of the liquid column above the limiter. st For the limiter well depth, D g-w The depth of the gas-liquid interface; The well depth of the limiter is determined based on the correspondence between the test well depth of the plunger and the well inclination angle determined by the determining unit.

7. A plunger structure for shale gas well plunger drainage and gas production analysis, characterized in that, It includes a plunger (1), a first buffer spring (3-1), a well inclination tester (2), a second buffer spring (3-2), and a fixing block (4). The plunger (1) has a hollow structure, and the well inclination tester (2) is set inside the hollow structure of the plunger (1). One end of the well inclination tester (2) is connected to the upper part of the plunger (1) through the first buffer spring (3-1), and the other end is connected to the fixed block (4) through the second buffer spring (3-2). The well inclination tester (2) is used to perform the method described in any one of claims 1 to 3.

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