CN114718515A - Design method for well wall of coal-bed gas well - Google Patents
Design method for well wall of coal-bed gas well Download PDFInfo
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- CN114718515A CN114718515A CN202110013893.3A CN202110013893A CN114718515A CN 114718515 A CN114718515 A CN 114718515A CN 202110013893 A CN202110013893 A CN 202110013893A CN 114718515 A CN114718515 A CN 114718515A
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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
- E21B43/006—Production of coal-bed methane
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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
Abstract
The application belongs to the technical field of coal bed gas development, and particularly relates to a coal bed gas well wall design method. According to the method, the consolidation propping agents are filled in the coal seam cracks formed by fracturing the coal seam gas well, and the consolidation propping agents can be mutually adhered and consolidated in the coal seam cracks to form a support strip, so that the consolidation propping agents are prevented from being embedded into the coal seam, the coal seam cracks are prevented from being closed and collapsed, and the method is realized: firstly, the desorption area of the coal bed is increased, so that the desorbed gas is greatly increased, and the gas production rate of a single well is improved; and secondly, the coal seam cracks become stable seepage channels with high flow conductivity, so that the permeability and the stability of the coal seam are enhanced, and high and stable yield of the coal seam gas well is further realized.
Description
Technical Field
The application belongs to the technical field of coal bed gas development, and particularly relates to a coal bed gas well wall design method.
Background
China has rich coal bed gas resources, but the yield of a single coal bed gas well is low, the exploitation amount of the coal bed gas is far lower than the expected target, and the technical problem is one of important factors for restricting the actual production capacity of the coal bed gas. The coal bed gas can be produced only through three links of desorption, diffusion and seepage, and the condition of low yield and low efficiency of the coal bed gas well can be caused by restriction of any link.
In the currently common coal bed gas well fracturing technology, conventional propping agents are mostly adopted to support coal bed fractures, but the conventional propping agents are easily embedded into a coal bed along with the outflow of formation fluid, so that the coal bed fractures are closed, and coal rock debris generated by a coal bed gas well wall (coal bed fractures) is easily peeled off into gaps among the conventional propping agents to block the coal bed fractures, so that the desorption area and seepage capacity of the coal bed fractures are greatly reduced, the desorption and seepage links in the coal bed gas extraction process are severely restricted, and the yield of the coal bed gas single well is low.
Disclosure of Invention
In view of this, the embodiment of the present application provides a method for designing a wall of a coal-bed gas well, so as to improve the productivity of the coal-bed gas well. The method comprises the following steps:
preparing a proppant which can be mutually adhered and consolidated in a coal seam fracture as a consolidation proppant, wherein coal particles can be adhered to the surface of the consolidation proppant;
filling consolidation proppant into coal bed cracks formed by fracturing of a coal bed gas well; the consolidation propping agents are mutually adhered in the coal seam cracks and are consolidated to form support strips so as to reinforce the wall of the coal seam gas well.
In one possible implementation, the filling of consolidated proppant into the fractures of the coal seam formed by the fracturing comprises: and squeezing the consolidation propping agent into the coal seam crack through the sand carrying fluid.
In one possible implementation, prior to extruding the consolidated proppant into the coal seam fracture with the sand-carrying fluid, the method further comprises: and (4) sieving the consolidated proppant.
In one possible implementation, before the consolidating proppant is squeezed into the coal seam fracture by the sand-carrying fluid, the method further comprises injecting a pad fluid into the coal seam gas well; after the consolidated proppant is squeezed into the coal seam fractures by the sand-carrying fluid, the method further comprises injecting a displacement fluid into the coal seam gas well.
In one possible implementation, the preparing the proppant as the consolidated proppant that will adhere to each other and consolidate in the fracture of the coal seam comprises: arranging a consolidation layer on the surface of the basic proppant so as to convert the basic proppant into a consolidated proppant; in the sand-carrying liquid water-containing environment, the consolidation layer can enable consolidation propping agents entering the coal seam fracture and contacting the surface to be mutually adhered, so that the consolidation propping agents entering the coal seam fracture form a consolidation propping strip.
In one possible implementation, disposing a bonding layer on the surface of the base proppant includes: mixing the basic proppant with the flowing phenolic resin to form a bonding layer consisting of the phenolic resin on the surface of the basic proppant.
In one possible implementation, before the surface of the base proppant is provided with the bonding layer, the method further comprises: and arranging a connecting layer consisting of a coupling agent on the surface of the basic propping agent.
In one possible implementation, after disposing the bonding layer on the surface of the base proppant, the method further includes: an isolation layer composed of an isolation agent is arranged on the surface of the basic propping agent, and the isolation layer can be dissolved in the aqueous environment of the sand-carrying fluid.
In one possible implementation, the base proppant is a rubber particle or a nutshell particle.
In one possible implementation, the method is applied to a target coal seam satisfying preset conditions, where the preset conditions include: the temperature of the target coal seam is not less than a preset temperature, and the preset temperature is a temperature which enables the isolation layer to be dissolved in the sand carrying liquid water-containing environment and enables the consolidation propping agents contacted with the surface to be mutually adhered and consolidated in the sand carrying liquid water-containing environment.
The beneficial effects brought by the technical scheme provided by the embodiment of the application at least comprise: according to the method, the consolidation propping agents are filled in the coal seam cracks formed by fracturing the coal seam gas well, and the consolidation propping agents can be mutually adhered and consolidated in the coal seam cracks to form a support strip, so that the consolidation propping agents are prevented from being embedded into the coal seam, the coal seam cracks are prevented from being closed and collapsed, and the method is realized: firstly, the desorption area of the coal bed is increased, so that the desorbed gas is greatly increased, and the gas yield of a single well is improved; and secondly, the coal seam cracks become stable seepage channels with high flow conductivity, so that the permeability and the stability of the coal seam are enhanced, and the high and stable yield of a single well is further realized.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 schematically illustrates an implementation principle of a design method for a well wall of a coal-bed gas well provided by the embodiment of the application;
FIG. 2 is a flow chart of a design method of a well wall of a coal bed gas well according to a first embodiment of the present application;
FIG. 3 is a flow chart of a design method of a well wall of a coal bed gas well according to a second embodiment of the present application;
FIG. 4 is a graph illustrating the effect of conventional proppant after filling a coal seam fracture;
FIG. 5 is a schematic representation of a structural diagram of a consolidated proppant provided in a second embodiment of the present application;
FIG. 6 is a graph illustrating the effect of consolidating proppant provided in the second embodiment of the present application after filling a fracture in a coal seam.
Detailed Description
To make the objects, technical solutions and advantages of the present application more clear, embodiments of the present application will be described in further detail below with reference to the accompanying drawings.
In one possible implementation environment, as shown in fig. 1, it is assumed that the circle at the inner part (the circle near point a) of the two concentric circles in fig. 1 is near a wellbore in the coal-bed gas well, the circle at the outer part (the circle near point B) is a point outside the drainage radius of the coal-bed gas well, and the straight line with the arrow is a possible movement track of the fluid in the coal bed. The fluid in the coal seam includes water and coal bed gas. When fluid flows in a coal seam fracture, the flow rate of the fluid passing through the point A (near the bottom of the well) is far greater than the flow rate at the point B (outside the drainage radius) under the same flow rate according to Darcy's law. Because the flow rate of the fluid at the point A is high, the coal bed at the point A is easy to produce coal dust and collapse due to long-term scouring of the high-speed fluid, so that formed coal bed cracks are blocked, and the seepage capability of the coal bed cracks is reduced. In addition, with the extension of coal bed gas well exploitation time, stratum stress can change, and because the coal bed gas is to the scouring action of crack both sides coal seam when flowing in the coal seam crack, the coal seam crack easily takes place to close or the coal petrography piece blocks up the coal seam crack easily to reduce the seepage flow ability of coal seam crack. Therefore, a design method for the well wall of the coal bed gas well, which can enhance the well wall strength of the coal bed gas well and can improve the seepage capability of coal bed cracks, is urgently needed.
A first embodiment of the present application provides a method for designing a wall of a coal bed gas well, as shown in fig. 2, the method includes:
step S101, preparing a proppant which can be mutually adhered and consolidated in a coal seam fracture as a consolidation proppant, wherein coal particles can be adhered to the surface of the consolidation proppant.
S102, filling consolidation proppant into a coal seam crack formed by fracturing a coal seam gas well; the consolidation propping agents are adhered to each other in the coal seam cracks and are consolidated to form support strips so as to reinforce the well wall of the coal seam gas well.
In one possible implementation, the filling of consolidated proppant into the fractures of the coal seam formed by the fracturing comprises: and squeezing the consolidation propping agent into the coal seam crack through the sand carrying fluid.
In one possible implementation, prior to extruding the consolidated proppant into the coal seam fracture with the sand-carrying fluid, the method further comprises: and (4) sieving the consolidated proppant.
In one possible implementation, before the consolidating proppant is squeezed into the coal seam fracture by the sand-carrying fluid, the method further comprises injecting a pad fluid into the coal seam gas well; after the consolidated proppant is squeezed into the coal seam fractures by the sand-carrying fluid, the method further comprises injecting a displacement fluid into the coal seam gas well.
In one possible implementation, the preparing the proppant as the consolidated proppant that will adhere to each other and consolidate in the fracture of the coal seam comprises: arranging a consolidation layer on the surface of the basic proppant so as to convert the basic proppant into a consolidated proppant; in the sand-carrying liquid water-containing environment, the consolidation layer can enable consolidation propping agents entering the coal seam fracture and contacting the surface to be mutually adhered, so that the consolidation propping agents entering the coal seam fracture form a consolidation propping strip.
In one possible implementation, disposing a bonding layer on the surface of the base proppant includes: mixing the basic proppant with the flowing phenolic resin to form a bonding layer consisting of the phenolic resin on the surface of the basic proppant.
In one possible implementation, before the surface of the base proppant is provided with the bonding layer, the method further comprises: and arranging a connecting layer consisting of a coupling agent on the surface of the basic propping agent.
In one possible implementation, after disposing the bonding layer on the surface of the base proppant, the method further includes: and arranging an isolating layer consisting of an isolating agent on the surface of the basic propping agent, wherein the isolating layer can be dissolved in the aqueous environment of the sand-carrying fluid.
In one possible implementation, the base proppant is a rubber particle or a nutshell particle.
In one possible implementation, the method is applied to a target coal seam satisfying preset conditions, where the preset conditions include: the temperature of the target coal bed is not less than a preset temperature, and the preset temperature is a temperature which enables the isolation layer to be dissolved in the sand-carrying liquid water-containing environment and enables the consolidation propping agents in surface contact to be mutually adhered and consolidated in the sand-carrying liquid water-containing environment.
According to the design method for the well wall of the coal bed gas well, the consolidation propping agents are filled in the coal bed cracks formed by fracturing the coal bed gas well, and the consolidation propping agents are mutually adhered and consolidated in the coal bed cracks to form supporting strips, so that the consolidation propping agents are prevented from being embedded into the coal bed, the coal bed cracks are prevented from being closed and collapsed, and the method is realized: firstly, the desorption area of the coal bed is increased, so that the desorbed gas is greatly increased, and the gas production rate of a single well is improved; and secondly, the coal seam cracks become stable seepage channels with high flow conductivity, so that the permeability and the stability of the coal seam are enhanced, and the high and stable yield of a single well is further realized.
A second embodiment of the present application provides a method for designing a wall of a coal bed gas well, as shown in fig. 3, the method includes:
step S201, preparing a proppant which can be mutually adhered and consolidated in the coal seam fracture as a consolidation proppant.
In the process of mining coal bed gas, because the permeability of a coal bed is generally low, the coal bed gas well is often required to be fractured so as to form more coal bed cracks, and thus the seepage capability of the coal bed is enhanced.
After the coal bed is fractured, due to factors such as stratum stress change and the scouring action of fluid in the coal bed on coal beds at two sides of the coal bed fracture along with the extension of production time, the coal bed fracture is easy to close or is easy to block the coal bed fracture due to coal rock fragments which are peeled off, so that the desorption area of the coal bed is reduced, the flow conductivity of the fracture is weakened (namely the seepage capability of the coal bed fracture is reduced), and the yield of the coal bed gas is reduced. In order to increase the stability of the coal seam fractures, the coal seam fractures formed by the fracturing may be filled with a proppant. The proppant can be filled into the coal seam fracture and has a propping effect on the coal seam fracture. However, if the coal seam fracture is propped only with conventional proppants, as shown in fig. 4, the conventional proppants are easily embedded into the coal seam under the action of formation stress to close the coal seam fracture as the production time is prolonged, and coal rock fragments generated in the production process are easily peeled off into the gaps of the proppants to block the coal seam fracture.
In one possible implementation, in order to avoid the above-mentioned problems occurring when filling the fractures of the coal seam with conventional proppants, a proppant in which surfaces adhere to each other and to which coal particles adhere can be prepared as the consolidated proppant, that is, the surfaces of the consolidated proppants that contact each other in the coal seam can adhere to each other and to which coal particles can adhere. The method for preparing the consolidated proppant may be to arrange (or coat) a consolidated layer composed of organic matters (such as phenolic resin) on the surface of a selected basic proppant (such as ceramsite or quartz sand), so that the basic proppant is converted into the consolidated proppant. Wherein, under the environment of carrying the sand fluid with water, the consolidation layer can make the consolidation propping agents entering the coal seam and contacting the surface adhere to each other, thereby leading the consolidation propping agents entering the coal seam to form a consolidation propping strip. Meanwhile, under the water-containing environment of the sand-carrying liquid, the consolidation layer can also enable coal particles to adhere to the surface of the consolidation proppant. In selecting the composition of the organic bonding layer, an organic substance satisfying the following conditions may be preferably selected as the composition of the bonding layer: (1) the chemical property is stable, and the acid and alkali resistance is suitable for the target coal seam; (2) the consolidation strength is high, and the stratum stress of the target coal seam can be borne; (3) the shrinkage rate is small in the consolidation process; (4) low cost and no pollution. The target coal seam refers to a coal seam corresponding to a coal-bed gas well with a borehole wall designed by applying the method provided by the embodiment.
In a possible implementation manner, taking the composition of the bonding layer as phenolic resin as an example, a bonding layer composed of phenolic resin can be arranged on the surface of the basic proppant by mixing the basic proppant with the flowing phenolic resin.
In one possible implementation, in order to improve the consolidation performance of the consolidated proppant, a curing agent may be added to the composition of the consolidated layer. For example, if the composition of the bonding layer is a phenolic resin, in order to improve the bonding performance of the phenolic resin film, the phenolic resin and the curing agent may be mixed in a certain mass ratio, and then the obtained mixture may be coated on the base proppant. The type of the curing agent and the mass ratio of the phenolic resin to the curing agent can be selected according to actual needs. For example, an aliphatic amine-based curing agent (e.g., diethylenetriamine) or an aromatic amine-based curing agent (e.g., m-xylylenediamine) may be selected, and the mass ratio of the phenol resin to the curing agent may be 3: 1.
In one possible implementation, in order to effectively adsorb the bonding layer to the surface of the base proppant, even though the bonding layer can effectively adhere to the surface of the base proppant, and further improve the bonding strength of the bonding proppant, a bonding layer composed of a coupling agent can be arranged on the surface of the base proppant before the bonding layer is coated on the surface of the base proppant. The coupling agent is a substance with two functional groups with different properties, the molecule of the coupling agent contains two groups with different chemical properties, one is an inorganophilic group, and the coupling agent is easy to chemically react with the surface of an inorganic substance (for example, hydroxyl can react with the surface of quartz sand to generate Si-O bonds and hydrogen bonds); the other is an organophilic group that is capable of chemically reacting with the organic (e.g., an amino group can react with a phenolic resin). In addition, the specific type of the coupling agent can be selected according to actual needs. For example, an aminosilane coupling agent may be selected to provide a tie layer, such as KH550 (NH), to the base proppant surface2CH2CH2CH2Si(OC2H5)3) And the like.
In a possible implementation manner, in order to prevent the consolidation of the consolidation proppant under the ground condition, that is, in order to prevent the consolidation proppant from being consolidated in the non-working state, the consolidation layer may be coated on the surface of the base proppant, and then an isolation layer composed of an isolation agent is disposed on the surface of the base proppant, that is, as shown in fig. 5, the surface of the consolidation proppant may simultaneously have a connecting layer, a consolidation layer and an isolation layer from inside to outside. The specific components of the release agent can be selected according to the actual production requirements, but generally, the release agent should satisfy the following conditions: (1) under the condition of normal temperature, the adhesion between the dried consolidation proppant particles can be prevented; (2) in a sand-carrying fluid aqueous environment, or as it were, after the surface of the consolidated proppant is wetted with water, dissolution occurs after a certain period of time (e.g., 2min or 3min, etc.), and does not affect the cohesion between the consolidated proppants, nor the surface of the consolidated proppant from adhering coal particles. Further, the release agent having stable performance, not increasing production cost, and having low contamination property can be selected as much as possible while satisfying the above conditions. For example, polyvinyl alcohol may be selected as the main component of the release agent.
It should be noted that after the release agent is dissolved in the aqueous environment of the sand-carrying fluid, the consolidation layer on the consolidation proppant can also be dissolved and the consolidation proppants with surfaces in contact with each other are adhered to each other to form a support strip, and while the consolidation proppants with surfaces in contact with each other form a support strip, the consolidation layer on the surface of the consolidation proppant can also be adhered to the coal seam in contact with each other, thereby preventing the coal seam from peeling off coal rock debris in the subsequent production process. After consolidating the proppant to form a stable support strip, the physical form (e.g., shape, etc.) of the support strip typically does not change.
In a possible implementation manner, after the bonding layer, the consolidation layer and the isolation layer are arranged on the surface of the base proppant, the obtained consolidated proppant can be dried by natural air drying or drying, and then stored for later use.
In one possible implementation, the base proppant may be rubber particles or nutshell particles having a diameter of 1.8mm to 2.5 mm. Wherein, when the base proppant is a rubber particle, the apparent density of the rubber particle may be 1g/cm3-1.5g/cm3. The main chemical components of the nutshell particles are cellulose, pentosan, lignin and the like, so that the density of the nutshell particles is often lower than that of the quartz sand proppant commonly used at present. In addition, phenolic mono-type monomers in the chemical composition of the nutshell particlesThe meta-and aldehyde-group structure may undergo condensation reaction with aldehydes, phenols, etc. Under the condition of heating or acidity, the phenolic resin can be subjected to condensation polymerization among hydroxymethyl, and the hydroxymethyl and phenol or substituted phenol at ortho-position and para-position to be crosslinked into a high polymer with high hardness, and the phenolic resin can be reacted with reactive groups in the nut shells, so that the compatibility of the nut shells and the resin is improved, and benzene rings in the resin can endow the new material compounded with the phenolic resin with higher rigidity. Therefore, when the nutshell particles are used as the basic proppant to be combined with the phenolic resin, a connecting layer does not need to be formed on the nutshell particles. When the rubber particles or the nut shell particles are used as the basic propping agent, the quality of the finally obtained consolidation propping agent can be reduced, so that the buoyancy of the consolidation propping agent is increased, and the problem that when the consolidation propping agent is filled in coal bed cracks formed by fracturing of a coal bed gas well, the consolidation propping agent is rapidly settled and accumulated in a well bottom or a primary crack due to the gravity of the consolidation propping agent and cannot enter a secondary crack, so that the support range of the consolidation propping agent is small and a good support effect cannot be achieved.
Step S202, filling consolidation propping agents into coal seam fractures formed by fracturing of the coal seam gas well, wherein the consolidation propping agents are mutually adhered in the coal seam fractures and are consolidated to form support strips so as to reinforce the well wall of the coal seam gas well.
After the consolidated proppant is prepared in step S201, the consolidated proppant may be squeezed into the coal seam fracture through the sand-carrying fluid, that is, the consolidated proppant is filled into the coal seam fracture formed by fracturing the coal seam gas well by using the sand-carrying fluid. The sand-carrying fluid can bring the consolidation proppant into the coal seam fracture. In addition, in order to protect the formation environment during the production process, a suitable type of base fluid of the sand-carrying fluid can be selected according to geological conditions and production requirements, and for example, clear water or deoiled sewage can be selected as the base fluid of the sand-carrying fluid.
In one possible implementation, to prevent the consolidated proppant from settling prior to being packed into the coal seam fracture, a viscosity modifier may be added to the sand-carrying fluid to increase the viscosity of the sand-carrying fluid. Generally speaking, the greater the viscosity of the sand carrying fluid, the greater the viscous resistance of the consolidated proppant particles in the sand carrying fluid, and the buoyancy and impact force of the fluid in the sand carrying fluid to the consolidated proppant particles increase with the increase of the viscosity of the sand carrying fluid, so that the settling velocity of the consolidated proppant becomes smaller. The larger the viscosity of the sand carrying liquid is, the stronger the sand carrying capacity of the sand carrying liquid is, so that the consolidation propping agent can be conveyed to a farther position, a long and gentle sand bank is formed, and the supporting area of the consolidation propping agent is enlarged. Therefore, the greater the viscosity of the sand-carrying fluid, the lower the settling rate of the consolidated proppant and the greater its horizontal migration rate. However, it should be noted that the viscosity of the sand-carrying fluid may not be too high, otherwise the flow rate of the sand-carrying fluid may be reduced, so that the consolidation proppant is accumulated and consolidated in the initial section of the coal seam fracture, and thus, a good supporting effect cannot be obtained. Therefore, before the consolidated proppant is filled into the coal seam fracture through the sand-carrying fluid, the proper viscosity of the sand-carrying fluid can be selected through a method of field examination and test, and the consolidated proppant can be squeezed into the coal seam fracture by using the sand-carrying fluid with the preset viscosity.
In addition, as the sand ratio is increased, the concentration of the consolidated proppant in the coal seam fracture is gradually increased, so that the interaction between the consolidated proppant particles is more severe. When the concentration of the consolidated proppant in the coal seam fracture is too high, the consolidated proppant may be consolidated in the initial section of the coal seam fracture and cannot enter a secondary fracture, and the consolidated proppant may also obstruct the flow of the subsequent consolidated proppant, so that the proppant has a smaller propping range and cannot achieve a good propping effect. Therefore, the sand ratio of the sand-carrying fluid should be taken into account when the consolidation proppant is squeezed into the coal seam fracture by the sand-carrying fluid, so as to prevent premature consolidation of the consolidation proppant in the coal seam fracture.
In a possible implementation manner, before the consolidation proppant is squeezed into the coal seam fracture through the sand carrying fluid, the consolidation proppant can be sieved to screen out the consolidation proppant with the diameter larger than a preset threshold value, so that large-particle-size impurities are prevented from being mixed into the consolidation proppant. The number of sieving can be selected according to the actual situation, for example, sieving can be performed twice or three times, and the like. In addition, the specific value of the preset threshold value can also be selected according to the actual production situation, for example, a standard 20-mesh sieve can be adopted to sieve the consolidated proppant.
In one possible implementation manner, a pad fluid can be injected into the coal-bed gas well to open the coal-bed crack before the consolidation propping agent is squeezed into the coal-bed crack by the sand-carrying fluid, and a displacement fluid can be injected into the coal-bed gas well to displace the consolidation propping agent into the coal-bed crack after the consolidation propping agent is squeezed into the coal-bed crack by the sand-carrying fluid.
After the consolidated proppant is filled into the coal seam fractures formed by fracturing the coal seam gas well and after the isolation layer on the surface of the consolidated proppant is dissolved in the aqueous environment of the sand-carrying fluid, the consolidated layer on the surface of the consolidated proppant can adhere the consolidated proppant on the surface contact to each other to form the support strip (as shown in fig. 6). The consolidation propping agent after the strips are formed is stronger in compressive property than the dispersed propping agent, and can be prevented from being embedded into a coal bed under the action of stratum stress, so that formed coal bed cracks are not easy to block or collapse, the well wall of a coal bed gas well can be reinforced, a seepage channel with high flow conductivity and stability is formed, and the single well yield of the current coal bed gas well is improved. The consolidation propping agent can prevent the coal seam crack from being closed, so that after the consolidation propping agent forms a stable support strip, the desorption area of the coal seam can be enlarged, and the current single-well reserve control range of the coal seam gas well is enlarged. In addition, since the shape of the base proppant is mostly circular or approximately circular, the shape of the consolidated proppant obtained after providing the connecting layer, the consolidated layer, and the spacer layer on the surface of the base proppant is also circular or approximately circular. When the surfaces of a plurality of round (or approximately round) consolidated proppants are contacted, the contact does not represent that all the surfaces of the plurality of consolidated proppants are contacted, namely, after the consolidated proppants in surface contact are consolidated to form a stable propping strip, the fluid in the fracture of the coal seam can still pass through gaps between the consolidated proppants, namely, after the consolidated proppants form a stable propping strip, the propping strip still maintains strong seepage capability. In order to enlarge the gaps of the support strip formed by the consolidated proppant, the proppant with the roundness and sphericity not lower than 0.6 can be selected as the basic proppant.
In a possible implementation manner, in order to further prevent the consolidation proppant from being consolidated before being put into the coal seam fracture, a preset condition may be set for a consolidation environment of the consolidation proppant, or, in other words, a preset condition may be set for an applicable environment of the coal seam gas well wall design method provided in this embodiment, that is, the coal seam gas well wall design method is applicable to a target coal seam meeting the preset condition. For example, when the surface of the consolidated proppant is coated with the isolation layer, since the main component of the isolation layer is generally organic matter, in order to dissolve the isolation layer on the surface of the consolidated proppant in the aqueous environment of the sand-carrying fluid, so that the consolidated proppant entering the fracture of the coal seam is adhered to form a support strip in the aqueous environment of the sand-carrying fluid, the preset conditions may be set as follows: the temperature of the target coal seam is not less than a preset temperature, and the preset temperature is a temperature which enables the isolation layer on the surface of the consolidation propping agent to be dissolved in the sand-carrying liquid water-containing environment and enables the consolidation propping agents contacted with the surface to be mutually adhered and consolidated in the sand-carrying liquid water-containing environment. The specific value of the preset temperature can be selected according to the actual working condition, for example, 30 degrees centigrade can be selected as the specific value of the preset temperature. In addition, it is also feasible to select proper organic matters as the components of the isolation layer and the consolidation layer according to the geological conditions of the current coal seam.
After appropriate preset conditions are set, the design method for the well wall of the coal-bed gas well is suitable for different fractured well types of the coal-bed gas well, such as a vertical well or a directional well.
According to the design method for the well wall of the coal-bed gas well, the consolidation propping agent is filled into the coal-bed cracks formed by fracturing the coal-bed gas well, so that the consolidation propping agent is consolidated in the coal-bed cracks to form stable supporting strips, the supporting capacity of the consolidation propping agent can be enhanced, and the consolidation propping agent is prevented from being embedded into the coal bed, so that the coal-bed cracks can be prevented from being closed and collapsed, a stable desorption surface and a seepage channel with high flow conductivity are formed, and the high yield and the stable yield of the coal-bed gas well are realized while the well wall of the coal-bed gas well is reinforced.
When the consolidation proppant is prepared, the connecting layer, the consolidation layer and the isolating layer are sequentially arranged on the surface of the basic proppant from inside to outside, so that the adhesion capability of the consolidation layer and the surface of the basic proppant can be enhanced, the consolidation strength of the consolidation proppant is further enhanced, and the consolidation of the consolidation proppant on the ground or in a shaft can be prevented. Through adopting rubber granule or nut shell granule as basic proppant, can alleviate the quality of the consolidation proppant that finally obtains to increase consolidation proppant self buoyancy, avoid consolidation proppant to subside fast because of self gravity and pile up, can make consolidation proppant enter into more coal seam fissures, thereby enlarge the support range of proppant, make consolidation proppant play good supporting effect.
By setting the preset conditions, the method for designing the well wall of the coal-bed gas well is suitable for the target coal bed meeting the preset conditions, can further prevent the consolidation proppant from being consolidated under the unnecessary condition, and can also promote the consolidation proppant to be consolidated under the appropriate condition to a certain extent.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. A design method for a well wall of a coal bed gas well is characterized by comprising the following steps:
preparing a proppant which can be mutually adhered and consolidated in a coal seam fracture as a consolidated proppant, wherein the surface of the consolidated proppant can be adhered with coal particles;
filling the consolidated proppant into coal bed fractures formed by fracturing the coal bed gas well; the consolidated proppants are adhered to each other in the coal seam cracks and are consolidated to form support strips so as to reinforce the well wall of the coal seam gas well.
2. The method of claim 1, wherein the filling consolidated proppant into the fractures of the coal seam formed by the fracturing comprises:
and extruding the consolidation proppant into the coal seam fracture through the sand carrying fluid.
3. The method of claim 2, further comprising, prior to extruding the consolidated proppant into a coal seam fracture with a sand-carrying fluid:
and (4) sieving the consolidated proppant.
4. The method of claim 2, further comprising injecting a pad fluid into the coal-bed gas well prior to the consolidating proppant being squeezed into the coal-bed fractures by the sand-carrying fluid;
after the consolidating proppant is squeezed into a coal seam fracture by a sand-carrying fluid, the method further comprises injecting a displacement fluid into the coal seam gas well.
5. The method of claim 1, wherein preparing a proppant as the consolidated proppant that will adhere to each other and consolidate in a coal seam fracture comprises:
arranging a consolidation layer on the surface of the basic proppant so as to convert the basic proppant into a consolidated proppant; wherein, in the sand-carrying fluid water-containing environment, the consolidation layer can enable the consolidation propping agents entering the coal seam fracture to be adhered with each other in surface contact, so that the consolidation propping agents entering the coal seam fracture form a consolidation propping strip.
6. The method of claim 5, wherein said disposing a bonding layer on the surface of the base proppant comprises:
and mixing the basic proppant with the flowing phenolic resin to form a bonding layer consisting of the phenolic resin on the surface of the basic proppant.
7. The method of claim 5, wherein prior to disposing the consolidating layer on the base proppant surface, the method further comprises:
and arranging a bonding layer consisting of a coupling agent on the surface of the basic propping agent.
8. The method of claim 5, wherein after disposing the consolidating layer on the surface of the base proppant, the method further comprises:
and arranging an isolating layer consisting of an isolating agent on the surface of the basic propping agent, wherein the isolating layer can be dissolved in the sand-carrying fluid aqueous environment.
9. The method of any one of claims 5-8, wherein the base proppant is a rubber particle or a nutshell particle.
10. The method of any one of claims 1 to 8, wherein the method is applied to a target coal seam meeting preset conditions, the preset conditions comprising: the temperature of the target coal seam is not less than a preset temperature, and the preset temperature is a temperature which enables the isolation layer to be dissolved in the sand-carrying fluid water-containing environment and enables the consolidation propping agents in surface contact to be mutually adhered and consolidated in the sand-carrying fluid water-containing environment.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110013893.3A CN114718515A (en) | 2021-01-06 | 2021-01-06 | Design method for well wall of coal-bed gas well |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202110013893.3A CN114718515A (en) | 2021-01-06 | 2021-01-06 | Design method for well wall of coal-bed gas well |
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| CN114718515A true CN114718515A (en) | 2022-07-08 |
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| CN202110013893.3A Pending CN114718515A (en) | 2021-01-06 | 2021-01-06 | Design method for well wall of coal-bed gas well |
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