CN115045645A - Process for improving effective reconstruction volume of ultra-deep high-temperature fractured reservoir - Google Patents
Process for improving effective reconstruction volume of ultra-deep high-temperature fractured reservoir Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a process for improving effective reconstruction volume of an ultra-deep high-temperature fractured reservoir, and relates to the technical field of reconstruction of the ultra-deep high-temperature fractured reservoir of an oil and gas reservoir. The invention comprises the following steps: s101, simulating the bottom temperature and the temperature in a crack under the conditions of different discharge capacities and different scales of fracturing fluids according to the temperature of a reservoir stratum tested by logging after a reconstruction section is determined; s102, determining the use concentration of the sand-carrying slick water thickening agent according to the simulated temperature field, and optimizing the reasonable use amount of the sand-carrying slick water thickening agent in the step to ensure that the sand-carrying slick water has better sand-carrying capacity at a certain temperature in a seam during construction; s103, designing the scale of the pad fluid and the sand adding amount, wherein the pad fluid stage makes small cracks and opens natural cracks by means of large-scale slick water. According to the invention, the sand-carrying slick water is selected, and the small-particle-size high-strength ceramsite is continuously added in the low-viscosity pad fluid stage to support the activated natural crack, so that the modified natural crack is ensured to have higher flow conductivity.
Description
Technical Field
The invention relates to the technical field of modification of a fractured reservoir of an ultra-deep high-temperature oil and gas reservoir, in particular to a process for improving the effective modification volume of the fractured reservoir of the ultra-deep high-temperature oil and gas reservoir.
Background
With the continuous expansion of oil and gas exploration and development to deep layers/ultra-deep layers, under the action of geological structure and compaction, a reservoir is more compact, the temperature is higher, and natural fractures are generally difficult to develop, so how to realize efficient transformation through an optimal transformation technology is an inevitable choice for deep layer/ultra-deep reservoir benefit exploration and development.
The volume modification technology is the latest reservoir modification technology formed under the guidance of modern modification theory, the core of the technology is that a complex fracture network system which is communicated with each other is established in a target reservoir by means of hydraulic fracturing, the fracture network system is different from a double-wing symmetrical fracture formed by the traditional modification technology, the fracture can be roughly regarded as a plane, the fracture system formed by the volume modification is a spatial three-dimensional structure, and the contact area between an artificial fracture and the reservoir is greatly increased. In order to realize volume transformation and increase effective transformation volume, the horizontal well segmented/clustered well completion transformation technology is mostly used.
However, volume modification is difficult to realize for single-layer modification of a vertical well, and natural fractures are difficult to develop due to the ultra-deep fractured reservoir, so how to open the natural fractures by activating the natural fractures and simultaneously pumping and injecting a propping agent by means of the natural fractures so as to effectively support the opened natural fractures and improve the flow conductivity of the natural fractures becomes a necessary means for realizing the effective volume modification of the ultra-deep high-temperature fractured reservoir.
In the prior art, the following data contents are searched for:
(1) chinese patent CN110761765A discloses a volume fracturing method for activating natural fractures in a large range. The method comprises the steps of performing acid pretreatment and low-viscosity slickwater pre-crack construction, then pumping powder injection ceramics (70-140 meshes, 140-210 meshes) to plug a main crack and extend forwards, then pumping gel fracturing fluid to improve the discharge capacity and achieve the purpose of improving the net pressure in the main crack, activating a natural crack communicated with the main crack, finally pumping high-viscosity gel sand-carrying fluid to support the main crack, communicating the activated natural crack through the main crack, and improving the reconstruction volume;
(2) chinese patent CN105317415 discloses a fracture network fracturing process, which is mainly characterized in that fracturing fluid such as slickwater or active water is adopted to squeeze and inject into the stratum in the early stage of fracturing, when the bottom pressure of a well is higher than the fracture pressure of the stratum, a main fracture is formed in the stratum near a shaft, then slickwater or active water fracturing fluid enters the stratum far away from the shaft, and a plurality of fractures are pressed at the far stratum to form a fracture network. After stable cracks are formed in the stratum, a low-concentration propping agent is added, at the later stage of fracturing, linear glue or cross-linked gel is used as fracturing fluid to carry the high-concentration propping agent, main cracks close to a shaft are filled, sand carrying fluid of the shaft is replaced into the stratum by clear water or slickwater, and fracturing construction is finished;
(3) chinese patent CN110454133 discloses a complex fracture network fracturing method capable of controlling approach and extension, which is characterized by comprising three steps, step 1, injecting a first pad fluid: viscosity of the first pad solution is 50mPa ≤, and the volume is 3m or less 3 Min; step 2, injecting a second pad fluid: viscosity of the second pad solution is 5mPa ≤, and the displacement is 10m or more 3 Min; step 3, injecting a sand carrying liquid: firstly, injecting sand carrying liquid prepared from 70-140 meshes of powder pottery; then injecting a sand carrying liquid prepared from 40-70 meshes of small ceramsite;
(4) in the literature, "research on opening rule of natural fracture under action of multistage fracturing induced stress" (oil drilling technology "in 1 st stage 2015), a stratum stress distribution calculation model in the fracturing process is deduced according to a rock mechanics theory and the stress state of the natural fracture, so that mechanical conditions for opening the natural fracture in tensile failure and shear failure are obtained. Research shows that the induced stress generated by multi-stage fracturing makes natural fracture opening difficult, the induced stress is increased, the pumping pressure required by natural fracture opening is increased, the induced stress and the pumping pressure are in a linear relation, and the influence of the induced stress is considered in actual fracturing design.
(5) In the document, "feasibility analysis of ultra-deep fractured sandstone gas formation volume fracturing" (natural gas industry, 2013, 9 th year), relevant research is performed by a method combining theory, indoor analysis and field experiment, a block is determined to accord with a sliding stress mechanism through experiments, ground stress modeling and the like, a natural fracture shear fracture mechanism is analyzed and researched by applying Moore coulomb's criterion, and quantitative research is performed on opening and expansion rules of multiple natural fractures developing to different degrees. The pressure acting on the natural fracture pores is proved to be in positive correlation with the ground construction pressure, after the pressure increment reaches a critical stress value, the natural fractures are easy to be sheared and damaged, the artificial fractures are easy to expand along the natural fractures which can be partially opened, the natural fractures which are partially in favorable directions cannot be opened, and the reservoir bed with undeveloped natural fractures is difficult to be subjected to sand fracturing.
(6) The literature, interaction and influence between hydraulic fractures and natural fractures (2016, 36 th period of science and engineering), is based on fracture mechanics theory, establishes a mechanical model of interaction between hydraulic fractures and natural fractures, and analyzes the expansion form of the hydraulic fractures in a natural fracture medium system after encountering the natural fractures. Research suggests that hydraulic fractures tend to cross natural fractures under conditions of high level of principal stress difference, high approach angle, and high interface friction; the hydraulic fracture is more easily trapped under conditions of low level principal stress difference, low approach angle and low interface friction. At the same time, the higher the net pressure within the hydraulic fracture, the easier the natural fracture will open.
The patent and literature researches indicate that in the existing fractured reservoir reconstruction, a large number of measures are taken to generate secondary fractures by means of natural fractures, the natural fractures are mainly activated by means of low-viscosity liquid, the low-viscosity liquid can enter a natural fracture system more easily, the fluid pressure in the natural fractures is increased to activate the natural fractures, the activation mode comprises shearing and opening activation, the main fractures are manufactured by high-viscosity liquid in the later period, the supported main fractures are communicated with the early-stage activated natural fractures, a fracture network structure is formed in the reservoir, and the reconstruction volume is increased.
Analysis of published patents and documents on the transformation of reservoirs containing natural fractures, particularly ultra-deep reservoirs containing natural fractures, low-viscosity liquid activates natural fractures mostly, and then high-viscosity liquid carries sand to make main fractures to open the natural fractures to form fracture network transformation. However, the technology neglects an important aspect, in the process of activating natural fractures by low-viscosity fluid, the low-viscosity fluid used at present does not have sand carrying capacity, so that the natural fractures opened by shearing or opening by tension cannot be effectively supported by a propping agent, the natural fractures are closed after the fracturing fluid is drained back, the flow conductivity of the fracturing fluid is extremely low, and even a large number of closed natural fractures do not have the flow conductivity required by oil and gas production. Under the condition, the early-stage low-viscosity liquid activated natural fracture is converted into an ineffective natural fracture, so that the effective modification volume is obviously reduced, and therefore, a new modification process technology is urgently needed to be created, the effectiveness of the opened natural fracture in the ultra-deep high-temperature fracture reservoir modification process is increased, and the effective modification volume is further increased.
Disclosure of Invention
In order to solve the problem that the effective modification volume of the existing ultra-deep high-temperature fractured reservoir is insufficient, the invention provides a novel modification process technology, by adopting novel sand-carrying slickwater, matching with the modification scale requirement of a target layer and the temperature field simulation in a shaft bottom and an artificial fracture, the viscosity of the sand-carrying slickwater thickening agent is optimized, the sand-carrying stability in a pre-liquid stage is ensured, after a small amount of non-sand-carrying slickwater is added, the low-sand-ratio (5-10%) sand-carrying slickwater is directly pumped, and the natural fracture is effectively supported after being opened while the slickwater activates the natural fracture; pumping and injecting the high-sand-ratio sand-carrying liquid of the alternating-current jelly at the later stage, and supporting the main crack while forming the main crack; and finally, the supported and opened complex natural fracture system is communicated by using the main fracture with high flow conductivity, so that a fracture system formed by the high-flow-conductivity main fracture and the supported natural fracture is formed, the effective modification volume of the ultra-deep high-temperature fractured reservoir can be obviously improved, and the modification effect is improved.
The invention specifically adopts the following technical scheme for realizing the aim, and has the core points that the sand-carrying slickwater is adopted to start the continuous sand adding with low sand ratio in the pre-liquid stage, support the opened natural crack and improve the effective reconstruction volume:
the specific scheme is a process for improving the effective modification volume of an ultra-deep high-temperature fractured reservoir, which comprises the following steps:
s101, simulating the bottom temperature and the temperature in a crack under the conditions of different discharge capacities and different scales of fracturing fluids according to the temperature of a reservoir stratum tested by logging after a reconstruction section is determined;
s102, determining the use concentration of the thickening agent of the portable sand-carrying slick water according to the simulated temperature field, and optimizing the reasonable use amount of the thickening agent of the portable sand-carrying slick water in the step to ensure that the portable sand-carrying slick water has better sand-carrying capacity at a certain temperature in a seam during construction;
s103, designing the scale of the pad fluid and the sand adding amount, wherein the pad fluid stage makes small gaps and opens natural cracks by means of large-scale slickwater, and simultaneously, high-strength ceramsite propping agent with low sand ratio and small particle size is added to prop the small gaps and the opened natural cracks;
s104, designing the scale and the sand adding amount of the gel fracturing fluid, wherein the high-temperature-resistant gel fracturing fluid is adopted in the later construction period, and construction is carried out at a high sand ratio of 20-30% to form a main crack connecting a shaft and a stratum, and a supported small crack and a supported natural crack are communicated at the same time;
s105, performing displacement operation, determining the using amount of displacement fluid according to the relation of 1 time of the volume of the shaft, stopping adding sand after completing sand addition according to the scale of the modification design, and performing displacement operation, wherein the front 50% of the displacement fluid is crosslinked gel fracturing fluid, in the process, a gel breaker is added, the rest 50% of the displacement fluid is removed, a fracturing fluid base fluid (non-crosslinked fracturing fluid) is adopted, in the process, the gel breaker is not added, the pump is stopped to measure the pressure drop after the displacement fluid with the volume of 1 time of the shaft is pumped, and the well is opened and drained back after 1.5-2 hours.
Further, in step S101, a deep position in the modified section is determined, the temperature of the reservoir at the deep position in the modified section is calibrated according to the temperature of the reservoir tested by logging, and is compared with the tested neighboring wells, and the actual temperature of the reservoir at the modified section is finally determined, wherein the calculation formula of the temperature of the reservoir at the deep position in the modified section is the temperature of the modified section (well logging test temperature + (depth of the deep-well logging test temperature point in the modified section) × temperature gradient, and frac simulation software is used to simulate the temperature ranges of the bottom and the inside of the fracture at different discharge capacities and different frac scales.
Further, in step S101:
the simulated displacement is 3m3/min, 4m3/min, 5m3/min and 6m3/min in sequence;
the fracture scale of the simulation was 300-1500 squares and was incremented every 300 squares.
Further, in step S102, the sand-carrying slick water is elastic sand-carrying, and when the viscosity is 15mpa @, the ceramsite sand-mixing liquid is 30-50 mesh, and when the static sand-carrying sand ratio is 10%, the ceramsite sand-mixing liquid is statically placed at normal temperature for 30min, and only a small amount of sedimentation occurs.
Further, the step S103 includes the following steps:
firstly, pumping and adopting non-sand-carrying slickwater, wherein the total amount of the non-sand-carrying slickwater is 10% of the total scale of the well modification liquid;
after the distance is 10% far away from the edge of the front end of the hydraulic fracture, the temperature in the fracture is gradually reduced to about 50% of the temperature of a reservoir, the sand-carrying slickwater-sand ratio is designed to be 2%, 4%, 6%, 8% and 10%, the sand-carrying slickwater-sand ratio is gradually increased, the liquid scale of each sand-carrying slickwater-sand ratio accounts for 35%, 25%, 15%, 10% and 5% of the total scale of the modification liquid, and the propping agent adopts 70-140-mesh high-strength ceramsite.
Further, in step S104:
firstly, preferably selecting 40-70 meshes and 30-50 meshes of high-strength ceramsite proppant which respectively account for 35 percent and 15 percent of the total sand adding amount of the modified well;
and then optimizing a guanidine gum cross-linked gel fracturing fluid system according to the temperature of the reservoir, so that the gel fracturing fluid meets the requirement of high sand ratio sand carrying under the temperature condition of the reservoir, the sand ratio of the ceramsite of 40-70 meshes and the ceramsite of 30-50 meshes is respectively 20% and 25%, and the high-strength support of the artificial main crack and the crack part is ensured, in the step S104, the cross-linked gel fracturing fluid is selected, and the gel breaker is added in the whole process.
Advantageous effects
1. According to the invention, the sand-carrying slick water is selected, and the small-particle-size high-strength ceramsite is continuously added in the low-viscosity pad fluid stage to support the activated natural crack, so that the modified natural crack is ensured to have higher flow conductivity.
2. According to the invention, the high-flow-guide main crack formed by the crosslinked gel fracturing fluid is utilized at the later stage to communicate and activate and obtain the supported natural crack, so that the effective modification volume is obviously improved.
3. The construction process has strong operability, the fracturing modification forms complex seams and is effectively controlled, and the difficulties of low utilization degree of natural fractures and insufficient effective modification volume of ultra-deep fractured reservoir modification are solved.
Drawings
FIG. 1 is a graph showing displacement and temperature variations in a second embodiment of the present invention;
FIG. 2 is a graph showing temperature changes of the sand-carrying liquid according to the second embodiment of the present invention;
fig. 3 is a construction graph in the second embodiment of the present invention.
Detailed Description
The core of the application is to provide a process for improving the effective reconstruction volume of the ultra-deep high-temperature fractured reservoir, and the purpose is to provide the process.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.
Example one
The process for improving the effective reconstruction volume of the ultra-deep high-temperature fractured reservoir provided by one embodiment of the invention comprises the following steps:
s101, after a modification section is determined, simulating the bottom hole temperature and the temperature in a crack under the conditions of different discharge capacities and different scales of fracturing fluids according to the reservoir temperature of a logging test;
after the reconstruction section is determined, firstly calculating the temperature of a reservoir at the middle and deep position of the reconstruction section, testing the temperature of the bottom of the well by combining logging, and if the point of the logging testing temperature is the adjacent area of the reconstruction section, calculating the middle and deep temperature of the reconstruction section according to the geothermal gradient of the well, wherein the calculation method comprises the following steps: the temperature of the transformation section is equal to logging test temperature + (the depth of the transformation section is the depth of a logging test temperature point) multiplied by the geothermal gradient;
after obtaining the reservoir temperature of the reconstruction section, simulating the reservoir temperature by adopting Fracpro-PT fracturing simulation software at the discharge capacity of 3m 3 /min、4m 3 /min、5m 3 /min、6 m3 In the/min state, transforming a temperature field at the bottom of the well and in the fracture of the section, simultaneously setting the scale of the simulated fracturing fluid to 300-1500 square, gradually increasing every 300 square, setting the ground temperature as the environmental temperature during local construction when carrying out simulation calculation, and giving out the discharge volume of 3-6m according to the simulation calculation result 3 The temperature distribution ranges of the bottom and the inside of the fracture and the temperature field distribution of the inside of the fracture under the conditions that the min and the scale of the modified liquid are 300-1500 are determined, and the temperature ranges of the front end and other parts of the hydraulic fracture are determined;
s102, determining the use concentration of a thickening agent of the portable sand-bearing slickwater according to a simulated temperature field, wherein the temperature resistance of the portable sand-bearing slickwater is less than 80 ℃, and the temperature of a modification interval of the ultra-deep high-temperature well generally exceeds 120 ℃, so that the temperatures in a shaft bottom and a hydraulic fracture in a reservoir during modification construction process need to be determined by adding the portable sand-bearing slickwater, and the use amount of the thickening agent needed by the portable sand-bearing slickwater is determined according to the temperature of the reservoir and the temperature distribution in the fracture during modification;
in step S102, the purpose of the step is to preferentially select a sand-carrying slickwater formula system after determining the temperature distribution in the bottom of the modification section and the hydraulic fracture during the modification construction period in step S101;
the sand-carrying slick water is a polymer high-elasticity slick water which is different from a conventional slick water system, the viscosity of the polymer high-elasticity slick water is higher than that of the conventional slick water, the slick water is in an un-emulsified state at normal temperature and normal pressure, the main temperature resistance and sand carrying capacity of the polymer high-elasticity slick water depends on the thickening agent amount of a polymer contained in an emulsion, the viscosity range is 15-45mpa & lt & gt/s, and liquids in the viscosity range, including slick water and fracturing fluid base fluid, generally do not have static sand carrying capacity;
the selected portable sand slick water is elastic sand carrying, static sand carrying is realized by virtue of the high elasticity, when the viscosity is 15mpa $, the 30/50-mesh ceramsite sand mixing liquid is prepared, when the static sand carrying sand ratio is 10%, the static placement is carried out for 30min at normal temperature, only a small amount of sedimentation occurs, and after the temperature is higher than 80 ℃, the static sedimentation speed is obviously increased. Optimizing and determining a formula of the portable sand slick water suitable for the pre-liquid stage according to the characteristics of the novel portable sand slick water and the temperature field distribution determined in the step one;
s103, designing the scale of the pad fluid and the sand adding amount, wherein the pad fluid stage makes small gaps and opens natural cracks by means of large-scale slickwater, and simultaneously, a high-strength ceramsite propping agent with low sand ratio and small grain size is added to prop the small gaps and the opened natural cracks;
after the step S101 and the step S102 are combined, after the reasonable formula of the portable sand-containing slickwater is determined by combining the first two steps (the step S101 and the step S102) in the step S103, the step S103 is to optimize the pump injection process of the portable sand-containing slickwater;
according to the temperature field distribution in the bottom reservoir hydraulic fracture simulated in the steps S101 and S102, the temperature of a region with 10% of the temperature in the front end of the hydraulic fracture is higher than 100 ℃, firstly, pumping and adopting non-sand-carrying slickwater, wherein the total amount of the non-sand-carrying slickwater is 10% of the total scale of the well modification liquid; the main function of the part of the slick water is to reduce the temperature of the front edge in the hydraulic fracture;
after the distance of 10% from the edge of the front end of the hydraulic fracture is kept away, the temperature in the fracture is gradually reduced to about 50% of the temperature of a reservoir stratum, the sand ratio of the portable sand-carrying slick water is designed to be 2%, 4%, 6%, 8% and 10%, the sand ratio is gradually increased, the liquid scales of the portable sand-carrying slick water and the sand ratio account for 35%, 25%, 15%, 10% and 5% of the total scale of the modification liquid, and the propping agent adopts 70-140-mesh high-strength ceramsite, has strong pressure resistance and can keep certain flow conductivity under the high stress condition;
the sand adding amount is calculated according to the actual sand adding liquid to sand adding sand ratio, the construction discharge capacity is calculated, an operation mode with limited pressure and unlimited discharge capacity is adopted according to the equipment operation capacity, the discharge capacity is improved to the greatest extent, the net pressure in a hydraulic fracture joint is improved, the natural opening purpose is achieved, meanwhile, high-strength small-particle-size ceramic grains carried by the sand-carrying slickwater under the low sand ratio support the opened natural fracture, the natural fracture opened in the pre-liquid stage keeps high flow conductivity after the construction is finished, and the effective modification volume is improved;
s104, designing the scale and the sand adding amount of the gel fracturing fluid, wherein the high-temperature-resistant gel fracturing fluid is adopted in the later construction period, and construction is carried out at a high sand ratio of 20-30% to form a main crack connecting a shaft and a stratum, and a supported small crack and a supported natural crack are communicated at the same time;
in the step S104, a cross-linked jelly sand-carrying stage transformation pumping program is designed, the stage is the transformation construction of a main sand-adding stage, the main purpose is to utilize the higher crack-making and sand-carrying capacity of jelly, after a natural crack is pressed open by carrying sand and sliding water in the step S103, a cross-linked jelly fracturing fluid is pumped and injected into the step S104 to form the main crack as a main part, the cross-linked jelly has higher viscosity and is difficult to enter the natural crack, the main crack with a certain width is mainly formed, the cross-linked jelly has higher sand-carrying capacity at the same time, a high-sand ratio large-particle-size propping agent can be carried, the required main crack flow-guiding capacity is determined according to the capacity target of a transformation well, and then the specific sand ratio and the propping agent particle size are determined;
in the production process of an oil-gas well, the closer the artificial main fracture is to a well shaft, the higher the required flow conductivity is, so that the sand adding process of the cross-linked gel fracturing fluid is designed, the main guiding idea is that firstly, a low sand ratio (10%) and a small-particle-size propping agent (40-70 meshes) are pumped, the sand ratio and the particle size of the propping agent are gradually increased, the sand ratio is increased by steps of 10%, 15%, 20% and 25%, theoretically, the required amount of each step is 40%, 30%, 20% and 10%, and the specific design is flexibly adjusted according to the actual conditions of different wells;
the particle sizes of the propping agents in different stages are respectively 70-100 meshes, 40-70 meshes, 30-50 meshes and 20-40 meshes; under the condition, the flow conductivity of the main crack formed after construction is in step change and is matched with the pressure gradient of fluid in the main crack and the required flow conductivity in the actual production process;
and (3) forming a fracture network system of an artificial main fracture and a natural fracture in the reservoir by the natural fractures opened in the main fracture communication step II with high flow conductivity, wherein the main fracture of the fracture network system has high flow conductivity, and the activated secondary natural fractures are supported by the proppant and have certain flow conductivity. The transformation process method greatly improves the effective transformation volume of the ultra-deep high-temperature fractured reservoir;
s105, performing displacement operation, determining the using amount of displacement liquid according to the relation of 1 time of the volume of the shaft, stopping adding sand after completing sand addition according to the scale of the modification design, and performing displacement operation, wherein the front 50% of the displacement liquid is crosslinked gel fracturing liquid, in the process, a gel breaker is added, the rest 50% of the displacement liquid is removed, a fracturing liquid base liquid is adopted, in the process, the gel breaker is not added, a pump is stopped to measure pressure drop after the displacement liquid with the volume of 1 time of the shaft is pumped, and the shaft is opened and drained back after 1.5-2 hours;
in step S105 of the invention, after the cross-linked gel is mainly added with sand according to the design in step S104, the replacement operation is started to complete the final pump injection construction of the reconstruction construction well;
the main purpose of the displacement operation is to use a non-sand-carrying fracturing fluid pump to inject the non-sand-carrying fracturing fluid to displace the high-sand-ratio sand-carrying fluid in the shaft to enter the stratum, so as to ensure that no sand-containing liquid exists in the shaft, no sand-containing liquid exists in the shaft after the well is closed, or little sand-containing liquid exists, and the shaft cannot be blocked due to ceramsite sedimentation in the shaft after the liquid in the shaft breaks gel;
meanwhile, the design of displacement liquid amount is reasonable, displacement cannot be performed, so that a water crack opening is provided with a proppant-free supporting seam, a dumpling wrapping phenomenon occurs, and the yield of the oil-gas well after modification is influenced;
therefore, when the displacement liquid volume is designed, the well bore volume from the well head to the perforation position is strictly calculated, and the displacement liquid volume injected by the pump is controlled according to the volume value. The front 30% of the displacement fluid is designed as crosslinked gel fracturing fluid, the viscosity of the fluid is the same as that of the sand-carrying fluid, so that the displacement fluid is ensured not to generate 'fingering' phenomenon in a shaft, piston-type uniform displacement is realized, and the gel breaker is completely added in the pumping process of the displacement fluid. Replacing 70% of the displacement liquid with a fracturing fluid base liquid, properly adjusting construction discharge according to construction pressure without adding a gel breaker, and ensuring that the displacement is normally finished;
and after the pumping of the displacement liquid is finished, the transformation of all liquid pumping of the well is finished, and the well is shut down and returned according to actual conditions.
Example two
By combining the process in the first embodiment, in the practical application, taking one deep well of a certain oil field in the west of China as an example, the transformation section of the well has the target zone vertical depth of 6500m, the well logging detection and the proximity comparison are carried out, the target zone well temperature is 158 ℃, the natural cracks of the transformation section are relatively developed, and the crack density is 2.8 cracks/m;
according to the method, step S101, firstly, simulating temperature field distribution in a well bottom and a hydraulic fracture under different construction discharge capacities, wherein the average temperature condition of the surface of a western mountain area where the well is located is set to be 10 ℃; according to the predicted construction displacement, the displacement is simulated to be 2-6m 3 At the time of/min, the lowest temperature at the bottom of the well is reduced to below 40 ℃, and the discharge capacity is 2m 3 At the time of/min, the temperature of the bottom of the well can still be reduced to below 60 ℃, so that the sand-carrying liquid can be judged to be difficult to desand at the bottom of the well due to insufficient temperature resistance;
the temperature field in the crack is simulated, and the construction displacement is simulated to be 4m 3 The temperature distribution in the crack under the/min condition is that the temperature of the area of about 10 percent of the transverse front end of the hydraulic crack is more than 100 ℃, and the temperature of the area of 15 percent of the longitudinal upper part and the longitudinal lower part of the hydraulic crack is more than 100 ℃ (see figure 1 and figure 2).
In step S102, the amount of priming solution is designed based on the temperature field distribution simulated in step S101.
See in particular the actual construction diagram of fig. 3.
In step S103, the area A is a pressure test stage before the well is transformed, well mouth equipment with temperature resistance of 140MPa is selected for the well, and the pressure test of the well mouth is 120MPa before the transformation. The pressure-resistant 140MPa fracturing equipment and the pressure test process of the wellhead are characterized in that the wellhead is closed, the lowest displacement pump is used for pumping, the pressure is increased to about 80MPa, and the presence or absence of visible puncture and leakage of the ground high-pressure pipeline and the wellhead is observed;
then starting the pump at the lowest discharge capacity, stopping the pump when the pressure is increased to 120MPa, and observing whether the high-pressure manifold and the well mouth have puncture or not;
then observing a pressure indication curve of the instrument panel for 10min, wherein the pressure drop is less than 5MPa, and the pressure test is qualified;
in FIG. 3, the pressure in the area A is reduced by about 3MPa within 10min, and the pressure test is qualified;
in the figure 3, the B area is the stage of reducing the temperature in the crack by replacing liquid, setting and pumping a preposed hydraulic crack and is 1.5m 3 Replacing liquid with/min discharge and sealing, increasing discharge to 4.5m 3 Pumping for about 10min per min, wherein the liquid quantity of the B area is about 15% of the total liquid quantity of the well reconstruction;
according to the simulation result of the step S101, the temperature at the bottom of the well and in the crack can be reduced to 40-50 ℃, so that a portable sand-carrying slickwater system capable of resisting the temperature of 70 ℃ is optimized, and the portable sand-carrying slickwater is implemented to add sand in the stage C;
according to the invention, the sand adding sand ratio of the sand-carrying slick water in the stage C is respectively 2.0-2.3%, 4.0-4.3%, 6.0-6.4%, 8.0-8.5% and 10-11%, and the liquid amount scales are respectively about 35%, 25%, 15%, 10% and 5%; the total liquid amount in the C stage was 208.5m 3 The total sand amount is 10.8m3, and the selected ceramsite is 70-140 meshes of small particle size and high strength (pressure resistance of 89MPa), and mainly aims to activate natural cracks by using low-viscosity portable sand slick water, and meanwhile, the ceramsite with the small particle size enters the natural cracks and supports the natural cracks, so that the flow conductivity of the modified natural cracks is improved, and invalid natural cracks after closing are avoided;
and S104, selecting the crosslinked gel fracturing fluid which can resist the temperature of 160 ℃ according to the actual temperature condition of a reservoir, wherein the sand ratio is designed to be 10-25%, the actual construction sand ratio is in the range, the highest sand ratio is 25%, the liquid volume accounts for about 40%, 30%, 20% and 10%, the particle sizes of the high-strength ceramsite propping agents are 70/100 meshes, 40/70 meshes, 30/50 meshes and 20/40 meshes, adding a gel breaker in the whole construction process of the C stage, and under the condition that the construction discharge capacity is 5m3/min, the highest construction pressure is 115MPa, the liquid volume of the stage is 214.8m3, the actual sand addition is 37.5m3, so that the construction is smooth.
And S105, the step is mainly a displacement pumping stage after sand adding construction is finished, and the stage is mainly to displace sand fracturing fluid contained in a shaft into a stratum by using the sand-free fracturing fluid, so that the shaft is prevented from being blocked by sand setting after the sand fracturing fluid contained in the shaft is broken. Stopping adding sand to the packing auger and pumping the crosslinked gel fracturing fluid after the crosslinked gel sand adding construction in the third step is finished, wherein the total volume of the shaft is 36m 3 The amount of the crosslinked gel fracturing fluid in the displacement fluid is 18m 3 And simultaneously, the addition amount of the gel breaker is doubled, the addition of the cross-linking agent is stopped after the gel displacement fluid is pumped, the fracturing fluid base fluid or the sand-carrying slick water is adopted as the displacement fluid until the displacement is finished, and the pump stopping pressure curve is collected according to the design requirement after the pump is stopped. Data was collected for post-compression analysis.
The process for improving the effective modification volume of the ultra-deep high-temperature fractured reservoir is an efficient modification method for improving the effective modification volume of the ultra-deep high-temperature fractured reservoir, and aims to support the activated natural fractures by selecting portable sand slick water and continuously adding small-particle-size high-strength ceramsite in a low-viscosity pad fluid stage, ensure that the modified natural fractures have higher flow conductivity, and communicate and activate the supported natural fractures by utilizing high-flow-conductivity main fractures formed by a cross-linked gel fracturing fluid in the later stage, so that the effective modification volume is remarkably improved.
The method is implemented on site in the oil field, and the adjacent wells are compared, so that the method has a good application effect.
The technology is implemented in a well BZ9-A of a birimu oil field Bozi block, and sand is added for 48.3m 3 The test before transformation shows that the oil pressure is 42.6MPa, the yield gas per day is 18.6 multiplied by 104m3/d, and no liquid is produced.
After the technology is implemented, the oil pressure of an oil nozzle with the thickness of 8mm is tested to be 74.2MPa, yield gas of 79.3X 104m 3 Compared with the flow before modification, the unimpeded flow after modification is increased by 4.8 times.
Compared with an adjacent well which has similar reservoir characteristics and is modified by adopting a conventional sand adding technology, the yield of the adjacent well exceeds 1.5 times, and the yield increasing effect is obvious by applying the technology, so that the practical effect of the technology is proved to be better. The technology can obviously improve the transformation effect of the ultra-deep high-temperature fractured reservoir.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to cover any modifications, equivalents, improvements, etc. within the spirit and scope of the present invention.
Claims (6)
1. A process for improving effective reconstruction volume of an ultra-deep high-temperature fractured reservoir is characterized by comprising the following steps:
s101, after a modification section is determined, simulating the bottom hole temperature and the temperature in a crack under the conditions of different discharge capacities and different scales of fracturing fluids according to the reservoir temperature of a logging test;
s102, determining the use concentration of the sand-carrying slick water thickening agent according to the simulated temperature field;
s103, designing the scale of the pad fluid and the sand adding amount, wherein the pad fluid stage makes small gaps and opens natural cracks by means of large-scale slickwater, and simultaneously, a high-strength ceramsite propping agent with low sand ratio and small grain size is added to prop the small gaps and the opened natural cracks;
s104, designing the scale and the sand adding amount of the gel fracturing fluid, wherein the high-temperature-resistant gel fracturing fluid is adopted in the later construction period, and construction is carried out at a high sand ratio of 20-30% to form a main crack connecting a shaft and a stratum, and a supported small crack and a supported natural crack are communicated at the same time;
s105, performing displacement operation, determining the using amount of displacement liquid according to the relation of 1 time of the volume of the shaft, stopping adding sand after completing sand addition according to the scale of the modification design, and performing displacement operation, wherein the front 50% of the displacement liquid is crosslinked gel fracturing liquid, in the process, a gel breaker is added, the rest 50% of the displacement liquid is removed, fracturing liquid base liquid is adopted, in the process, the gel breaker is not added, the pump is stopped to measure the pressure drop after the displacement liquid with the volume of the shaft being 1 time of the volume of the shaft is pumped, and the well is opened and drained back after 1.5-2 hours.
2. The process of claim 1, wherein in step S101, the deep position in the modified section is determined, the temperature of the reservoir at the deep position in the modified section is calibrated according to the temperature of the reservoir tested by logging, and compared with the tested neighboring wells, and the actual temperature of the reservoir in the modified section is finally determined, and the calculation formula of the temperature of the reservoir at the deep position in the modified section is the temperature of the modified section + (the depth of the deep-logging testing temperature point in the modified section) x the temperature gradient of the earth, and the bottom hole and the internal temperature range of the fracture at different displacement and different fracturing scales are simulated by using Fracpro-PT simulation software.
3. The process for increasing the effective reconstruction volume of an ultra-deep high-temperature fractured reservoir of claim 2, wherein in the step S101:
the simulated displacement is 3m3/min, 4m3/min, 5m3/min and 6m3/min in sequence;
the fracture scale of the simulation was 300-1500 squares and was incremented every 300 squares.
4. The process of claim 1, wherein in the step S102, the sand-carrying slickwater is elastic sand-carrying, when the viscosity is 15mpa & S, the ceramsite sand-mixing liquid is 30-50 meshes, and when the static sand-carrying sand ratio is 10%, the sample is statically placed at normal temperature for 30min, and only a small amount of sedimentation occurs.
5. The process for improving the effective reconstruction volume of the ultra-deep high-temperature fractured reservoir according to claim 1, wherein the step S103 comprises the following steps:
firstly, pumping and adopting non-sand-carrying slickwater, wherein the total amount of the non-sand-carrying slickwater is 10% of the total scale of the well modification liquid;
after the distance is 10% far away from the edge of the front end of the hydraulic fracture, the temperature in the fracture is gradually reduced to about 50% of the temperature of a reservoir, the sand-carrying slickwater-sand ratio is designed to be 2%, 4%, 6%, 8% and 10%, the sand-carrying slickwater-sand ratio is gradually increased, the liquid scale of each sand-carrying slickwater-sand ratio accounts for 35%, 25%, 15%, 10% and 5% of the total scale of the modification liquid, and the propping agent adopts 70-140-mesh high-strength ceramsite.
6. The process for increasing the effective reconstruction volume of an ultra-deep high temperature fractured reservoir of claim 1, wherein in the step S104:
firstly, preferably selecting 40-70 meshes and 30-50 meshes of high-strength ceramsite proppant which respectively account for 35 percent and 15 percent of the total sand adding amount of the modified well;
and then optimizing a guanidine gum crosslinked gel fracturing fluid system according to the reservoir temperature, so that the gel fracturing fluid meets the requirement of carrying sand with high sand ratio under the reservoir temperature condition, and the sand ratio of the 40-70-mesh ceramsite is 20 percent and the sand ratio of the 30-50-mesh ceramsite is 25 percent respectively.
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