Fracturing method for reducing friction composite weighting

Abstract

The invention discloses a fracturing method for reducing friction composite weighting. The method comprises the steps that the construction displacement value in the fracturing process is obtained in real time; under the conditions that the construction displacement value is located in the initial displacement range, the construction displacement value is smaller than a first displacement threshold value after setting of the packer, and the first displacement threshold value, the second displacement threshold value, the third displacement threshold value, the fourth displacement threshold value and the fifth displacement threshold value are reached, the construction displacement value is determined to be within the initial displacement range; a first fracturing fluid, a second fracturing fluid, a third fracturing fluid, a fourth fracturing fluid, a fifth fracturing fluid, a sixth fracturing fluid and a seventh fracturing fluid are pumped into the shaft, the fracturing fluids comprise at least one of a first solution, a second solution or a propping agent, and the volume ratios of the first solution, the second solution or the propping agent in the fracturing fluids are different. Under the state of high construction displacement, the construction risk is reduced, the liquid friction resistance is effectively reduced, and the purpose of reducing the wellhead pressure is achieved.

Description

Technical Field

[0001] The present invention relates to the field of ultra-deep oil and gas reservoir transformation in oil and gas field development, and in particular to a fracturing method for reducing friction and compound weighting. Background Art

[0002] my country is rich in deep / ultra-deep oil and gas resources and has become an important strategic successor area for oil and gas resources. However, the deeper the target reservoir, the stronger the compaction effect, the higher the ground stress, and the limited completion string. As a result, problems such as high construction pressure, limited displacement and reconstruction scale are faced during the transformation process. The existing technology solves this problem by adopting high-efficiency weighted fracturing fluid. However, in fact, with the increase of construction displacement, the effect of weighted fracturing fluid on reducing wellhead pressure decreases significantly, that is, the pressure-reducing ability of weighted fracturing fluid is inversely correlated with the construction displacement. Research and analysis show that this is because the liquid friction resistance is high under high construction displacement, which will offset the pressure-reducing effect of weighted fracturing fluid on the wellhead. Based on this, while ensuring construction safety, it is urgent to provide a method to reduce liquid friction resistance under high construction displacement. Summary of the Invention

[0003] In the Tarim Kuche piedmont, the southern edge of Junggar, and northwest Sichuan, deep / ultra-deep oil and gas exploration has achieved significant breakthroughs and profitable development. PetroChina's Tarim Oilfield and Southwest Oil and Gas Field have deployed 10,000-meter exploration wells. In the actual development process, existing technology uses weighted fracturing fluid to reduce wellhead pressure. The fracturing fluid used in the fracturing construction process is generally based on a single soluble inorganic salt solution. The density of the fracturing fluid under different concentrations of soluble inorganic salt solution is different. In fact, the density of the soluble inorganic salt solution fracturing fluid can reach up to 1.7g / cm 3 -2.0g / cm 3 According to the transformation requirements of ultra-deep wells (i.e. oil and gas wells with a depth of more than 6500m), the density of the soluble inorganic salt solution fracturing fluid is required to be no more than 1.5g / cm 3 In the actual fracturing construction process, the density of soluble inorganic salt solution fracturing fluid is generally 1.15g / cm 3 -1.35g / cm 3 Theoretically, the density is 1.5g / cm 3 The soluble inorganic salt solution fracturing fluid can reduce the wellhead pressure by 30Mpa, greatly reducing the risk of sand fracturing construction. However, in the process of ultra-deep high-stress tight reservoir reconstruction, it was found that with the increase of construction displacement, the soluble inorganic salt solution fracturing fluid's effect on reducing wellhead pressure decreased significantly, that is, the pressure-reducing ability of the soluble inorganic salt solution fracturing fluid is inversely correlated with the construction displacement. After collecting data and analyzing it, it was found that the construction displacement was increased to 3.5m 3 / min or more, the depressurization effect of the inorganic salt solution fracturing fluid on the wellhead basically disappears. This is because the friction coefficient of the soluble inorganic salt solution fracturing fluid of a single material is positively correlated with its density, that is, the higher the density of the weighted fracturing fluid, the higher its friction coefficient. Existing studies have shown that the total friction resistance of the liquid pipe flow is proportional to the friction coefficient and the square of the displacement of the weighted fracturing fluid. Therefore, as the friction coefficient of the weighted fracturing fluid increases and the construction displacement increases, its total friction resistance increases, which in turn leads to the depressurization effect of the wellhead at a higher displacement, and the friction resistance offsets each other, which is ultimately manifested as an operation displacement exceeding 3.5m 3 / min, the depressurizing effect of the inorganic salt solution fracturing fluid on the wellhead basically disappears.

[0004] In view of the above problems, the present invention is proposed to provide a fracturing method that reduces friction and composite weighting, which overcomes the above problems or at least partially solves the above problems.

[0005] In a first aspect, an embodiment of the present invention provides a fracturing method for reducing frictional drag and composite weighting, comprising:

[0006] Real-time acquisition of the operation displacement value during the fracturing process;

[0007] When the operation displacement value is within the initial displacement range, pumping a first fracturing fluid, wherein the first fracturing fluid comprises the first solution and the second solution in a first preset volume ratio; the first solution is a soluble inorganic salt solution, and the second solution is a solid phase fracturing fluid;

[0008] After the packer is set and the operation displacement value is less than the first displacement threshold, pumping a second fracturing fluid, wherein the second fracturing fluid includes the first solution and the second solution in a second preset volume ratio;

[0009] When the construction displacement value reaches the first displacement threshold, pumping a third fracturing fluid, wherein the third fracturing fluid includes the first solution and the second solution in a third preset volume ratio;

[0010] When the construction displacement value reaches a second displacement threshold, pumping a fourth fracturing fluid, wherein the fourth fracturing fluid includes the first solution and the second solution in a fourth preset volume ratio;

[0011] When the construction displacement value reaches a third displacement threshold, pumping a fifth fracturing fluid, wherein the fifth fracturing fluid comprises a proppant and a fifth preset volume ratio of the first solution to the second solution;

[0012] When the construction displacement value reaches a fourth displacement threshold, pumping a sixth fracturing fluid, wherein the sixth fracturing fluid comprises a proppant and a sixth preset volume ratio of the first solution to the second solution;

[0013] When the construction displacement value reaches a fifth displacement threshold, pumping a seventh fracturing fluid, wherein the seventh fracturing fluid includes the second solution and a proppant;

[0014] The initial displacement range, the first displacement threshold, the second displacement threshold, the third displacement threshold, the fourth displacement threshold, and the fifth displacement threshold increase in sequence.

[0015] In one embodiment, the volume proportion of the first solution in the first fracturing fluid is higher than that of the second solution.

[0016] In one embodiment, the volume proportion of the first solution in the second fracturing fluid is higher than that of the second solution, and the volume proportion of the first solution in the second fracturing fluid is lower than that in the first fracturing fluid.

[0017] In one embodiment, the volume proportion of the first solution in the third fracturing fluid is higher than that of the second solution, and the volume proportion of the first solution in the third fracturing fluid is lower than that of the second fracturing fluid.

[0018] In one embodiment, the volume proportion of the first solution in the fourth fracturing fluid is lower than that of the second solution.

[0019] In one embodiment, the diameter of the proppant in the fifth fracturing fluid is within a first preset diameter range;

[0020] The volume proportion of the first solution in the fifth fracturing fluid is lower than that of the second solution; and the volume proportion of the first solution in the fifth fracturing fluid is lower than that in the fourth fracturing fluid.

[0021] In one embodiment, the diameter of the proppant in the sixth fracturing fluid is within a second preset diameter range;

[0022] The volume proportion of the first solution in the sixth fracturing fluid is lower than that of the second solution; and the volume proportion of the first solution in the sixth fracturing fluid is lower than that in the fifth fracturing fluid;

[0023] The sand-to-liquid ratio in the sixth fracturing fluid is higher than the sand-to-liquid ratio in the fifth fracturing fluid, where the sand-to-liquid ratio is the volume ratio of proppant to liquid in the fracturing fluid.

[0024] In one embodiment, the seventh fracturing fluid is composed of the second solution and a proppant with a third preset diameter range; the diameter of the proppant in the seventh fracturing fluid is within the third preset diameter range;

[0025] The sand-to-liquid ratio in the seventh fracturing fluid is higher than the sand-to-liquid ratio in the sixth fracturing fluid.

[0026] In one embodiment, the density of the first solution is 1.5 g / cm 3 .

[0027] In one embodiment, the second solution comprises solid spherical particles and jelly fracturing fluid.

[0028] The density of the second solution is the same as that of the first solution.

[0029] In one embodiment, the particle size of the solid spherical particles is 200 mesh, and the solid spherical particles are insoluble.

[0030] In one embodiment, the volume ratio of the first solution to the second solution in the first fracturing fluid is nine to one;

[0031] The volume ratio of the first solution to the second solution in the second fracturing fluid is eight to two;

[0032] The volume ratio of the first solution to the second solution in the third fracturing fluid is six to four;

[0033] The volume ratio of the first solution to the second solution in the fourth fracturing fluid is four to six;

[0034] The volume ratio of the first solution to the second solution in the fifth fracturing fluid is 2 to 8; the sand-to-liquid ratio of the fifth fracturing fluid is 10%;

[0035] The volume ratio of the first solution to the second solution in the sixth fracturing fluid is 1:9; the sand-to-liquid ratio of the sixth fracturing fluid is 15%;

[0036] The sand-to-liquid ratio of the seventh fracturing fluid is 20%.

[0037] In one embodiment, the proppant is ceramsite.

[0038] The beneficial effects of the above technical solutions provided by the embodiments of the present invention include at least:

[0039] The fracturing method for reducing the composite aggravation of friction provided by the embodiment of the present invention obtains the real-time construction displacement value during the fracturing process, and pumps the corresponding proportion of fracturing fluid into the wellbore according to the numerical range of the construction displacement value. Specifically, when the construction displacement value is within the initial displacement range, after the packer is sealed and is less than the first displacement threshold, reaches the first displacement threshold, reaches the second displacement threshold, reaches the third displacement threshold, reaches the fourth displacement threshold, and reaches the fifth displacement threshold, the first fracturing fluid, the second fracturing fluid, the third fracturing fluid, the fourth fracturing fluid, the fifth fracturing fluid, the sixth fracturing fluid, and the seventh fracturing fluid are pumped into the well respectively, wherein the first displacement threshold, the second displacement threshold, the third displacement threshold, the fourth displacement threshold, and the fifth displacement threshold are respectively The quantity threshold increases successively, and by controlling the components of the first solution, the second solution and the proppant and the proportion of each component, the first fracturing fluid, the second fracturing fluid, the third fracturing fluid, the fourth fracturing fluid, the fifth fracturing fluid, the sixth fracturing fluid and the seventh fracturing fluid are configured, so that fracturing fluids with different component ratios can be selected at different construction displacements, so that different components can play their respective advantages and effectively reduce the construction pressure of ultra-deep high-stress reservoir reconstruction. For ultra-deep and high-stress construction wells, combined weighted fracturing technology can be implemented according to different construction displacements. As the construction displacement increases, the ratio of soluble inorganic salt fracturing fluid to solid-phase fracturing fluid is adjusted, so that the resistance reduction rate will not decrease regardless of low or high construction displacements, and the fracturing fluid can maintain the same effect of reducing the construction pressure on the wellhead.

[0040] In addition, since soluble inorganic salt fracturing fluid and solid phase fracturing fluid have their own friction characteristics, the friction coefficient of soluble inorganic salt fracturing fluid is high at high construction displacement, but the construction risk is low at low construction displacement. Since solid phase fracturing fluid contains a large amount of solid particles, the risk of solid sedimentation (sand plugging) is high at low construction displacement, which can easily block the wellbore and cause construction accidents. Therefore, under low construction displacement, soluble inorganic salt fracturing fluid is mainly used. As the construction displacement increases, the proportion of soluble inorganic salt fracturing fluid is gradually reduced, and the proportion of solid phase fracturing fluid is simultaneously increased to ensure that the resistance reduction rate of the fracturing fluid pumped into the wellbore will not decrease, and the fracturing fluid has the same effect of reducing construction pressure on the wellhead at low and high construction displacements.

[0041] Furthermore, the solid-phase fracturing fluid uses solid insoluble matter as a weighting agent and adopts solid-phase weighting material technology. Since the solid phase formed by the dispersion of solid particles in water is insoluble in water, it does not affect the extension of the thickener molecules dissolved in water to form a long-chain structure, thereby not affecting the overall resistance reduction performance of the fracturing fluid.

[0042] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

[0043] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0045] Figure 1 This is a flow chart of a fracturing method for reducing frictional drag and compound aggravation according to an embodiment of the present invention;

[0046] Figure 2 Schematic diagram of the construction curve of the construction well in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0048] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0049] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0050] Example 1

[0051] In order to solve the problem of reducing the friction resistance of the fracturing fluid under high operation displacement in the prior art, the embodiment of the present invention provides a fracturing method for reducing the friction resistance and compound aggravation, and the process is referred to Figure 1 As shown, the following steps are included:

[0052] Step S101: obtaining the operation displacement value during the fracturing process in real time;

[0053] Step S102: When the operation displacement value is within the initial displacement range, pumping a first fracturing fluid, the first fracturing fluid comprising a first solution and a second solution in a first preset volume ratio; the first solution is a soluble inorganic salt solution, and the second solution is a solid phase fracturing fluid;

[0054] Step S103: After the packer is set and the operation displacement value is less than the first displacement threshold, pumping a second fracturing fluid, the second fracturing fluid comprising the first solution and the second solution in a second preset volume ratio;

[0055] Step S104: when the operation displacement value reaches the first displacement threshold, pumping a third fracturing fluid, the third fracturing fluid comprising the first solution and the second solution in a third preset volume ratio;

[0056] Step S105: when the operation displacement value reaches the second displacement threshold, pumping a fourth fracturing fluid, the fourth fracturing fluid comprising the first solution and the second solution in a fourth preset volume ratio;

[0057] Step S106: when the construction displacement value reaches the third displacement threshold, pumping a fifth fracturing fluid, the fifth fracturing fluid comprising a proppant and a first solution and a second solution in a fifth preset volume ratio;

[0058] Step S107: when the construction displacement value reaches the fourth displacement threshold, pumping a sixth fracturing fluid, the sixth fracturing fluid comprising a proppant and a first solution and a second solution in a sixth preset volume ratio;

[0059] Step S108: When the operation displacement value reaches the fifth displacement threshold, pumping a seventh fracturing fluid, the seventh fracturing fluid including the second solution and a proppant;

[0060] The initial displacement range, the first displacement threshold, the second displacement threshold, the third displacement threshold, the fourth displacement threshold and the fifth displacement threshold increase in sequence.

[0061] By controlling the components of the first solution, the second solution, and the proppant and the proportions of each component, a first fracturing fluid, a second fracturing fluid, a third fracturing fluid, a fourth fracturing fluid, a fifth fracturing fluid, a sixth fracturing fluid, and a seventh fracturing fluid are configured, and real-time operation displacement is obtained. When the operation displacement value is within the initial displacement range, after the packer is set and is less than the first displacement threshold, when the first displacement threshold is reached, when the second displacement threshold is reached, when the third displacement threshold is reached, when the fourth displacement threshold is reached, and when the fifth displacement threshold is reached, the first fracturing fluid, the second fracturing fluid, the third fracturing fluid, the fourth fracturing fluid, the fifth fracturing fluid, the sixth fracturing fluid, and the seventh fracturing fluid are respectively pumped into the wellbore, so that fracturing fluids with different components or their proportions are pumped into the wellbore according to the operation displacement. Since the friction coefficients of different components are different, the different components can play their respective advantages, effectively reducing the operation pressure of ultra-deep and high-stress reservoir reconstruction.

[0062] The “initial displacement range” refers to a numerical range, indicating that the construction displacement value is in a low displacement state after the fracturing operation begins. The initial displacement range, the first displacement threshold, the second displacement threshold, the third displacement threshold, the fourth displacement threshold and the fifth displacement threshold can be pre-set empirical values. For example, the initial displacement range can be 0.5m 3 / min-0.8m 3 / min, the first displacement threshold can be 1.0m 3 / min, the second displacement threshold can be 2.0m 3 / min, the third displacement threshold can be 3.0m 3 / min, the fourth displacement threshold can be 4.0m 3 / min, the fifth displacement threshold can be 5.0m 3 / min. In fact, various thresholds or value ranges can be set according to actual construction conditions, and the embodiment of the present invention does not limit this.

[0063] To reduce the friction of the fracturing fluid under high operation displacement, a thickener (a thickener is a drag reducing agent, also known as non-weighted fracturing fluid) can be added to the fracturing fluid to achieve this. This is because the thickener can swell in water and form a linear long chain structure after expansion. The linear long chain structure extends in water. In the case of pipe flow, it can prevent turbulence in the pipe flow (turbulence is an important cause of pipe flow friction), thereby reducing friction. The inventors of the present invention have found that after the soluble inorganic salt solution is dissolved in water, its salt ion concentration is high, which prevents the thickener from The dissolution and extension of the linear long-chain structure in water loses the restriction of the linear long-chain structure, which makes the pipe flow fluid prone to phenomena and significantly increases the liquid friction. Therefore, the fracturing fluid prepared with a soluble inorganic salt solution as a weighting agent has a significantly reduced friction coefficient as the density of the fracturing fluid increases. Based on this, the inventors of the present invention use a soluble inorganic salt solution (i.e., the first solution) and a solid insoluble substance (the second solution contains a solid insoluble substance) to jointly prepare a weighted fracturing fluid to obtain a composite weighted fracturing fluid to reduce the wellhead pressure.

[0064] In some optional embodiments, the first solution is a soluble inorganic salt solution, for example, sodium chloride, potassium chloride, sodium bromide, calcium bromide, potassium bromide, sodium nitrate, potassium formate or calcium chloride and other soluble inorganic salts can be selected. By changing the concentration of the soluble inorganic salt solution, the density of the fracturing fluid can be changed. Generally speaking, a low-density weighted solution refers to a solution with a density of less than 1.2 g / m 3 Soluble inorganic salt solution, medium and high density weighted solution refers to a density greater than or equal to 1.2g / m 3 of soluble inorganic salt solution,

[0065] The second solution is a solid-phase fracturing fluid, which can use solid insoluble substances as weighting agents. The solid phase selected in the embodiment of the present invention is high-strength solid particles with a particle size of 200 mesh. The solid particles are insoluble in acid and alkali fracturing fluids. Since the solid phase formed by the dispersion of the solid particles in water is insoluble in water, it does not affect the extension of the thickener molecules dissolved in water to form a linear long-chain structure, thereby reducing the impact on the overall drag reduction performance of the liquid and ensuring that the solid-phase fracturing fluid maintains a similar drag reduction rate as the non-weighted fracturing fluid. The inventors of the present invention concluded through continuous oil tubing friction tests that the drag reduction performance of the solid-phase fracturing fluid is close to that of the non-weighted fracturing fluid. Compared with the drag reduction rate of a soluble inorganic salt solution fracturing fluid with the same density, the drag reduction rate of the solid-phase fracturing fluid is increased by 20%-60%.

[0066] In some optional embodiments, before the fracturing operation, a first solution (soluble inorganic salt fracturing fluid) and a second solution (solid phase fracturing fluid) can be prepared in advance. The density of the first solution is 1.5 g / cm 3 The second solution comprises solid spherical particles and a gel fracturing fluid, wherein the particle size of the solid spherical particles is 200 mesh, the solid spherical particles are insoluble, and the density of the second solution is the same as that of the first solution.

[0067] In some optional embodiments, the construction displacement value is obtained in real time from the start of the fracturing construction, and the construction displacement value is within the initial displacement range (0.5m 3 / min-0.8m 3 / min), pumping the first fracturing fluid into the wellbore to replace the original completion fluid in the wellbore, so that the wellbore is filled with the first fracturing fluid, and the volume proportion of the first solution in the first fracturing fluid is higher than that of the second solution;

[0068] After the ball is dropped into the packer, that is, after the packer is set, and the operation displacement value is less than the first displacement threshold (1.0m 3 / min), the second fracturing fluid is pumped into the wellbore to replace the first fracturing fluid, the volume proportion of the first solution in the second fracturing fluid is higher than that of the second solution, and the volume proportion of the first solution in the second fracturing fluid is lower than that in the first fracturing fluid.

[0069] The construction displacement gradually increases, and when the construction displacement value reaches the first displacement threshold (1.0m 3 / min), the third fracturing fluid is pumped into the wellbore to replace the second fracturing fluid, the volume proportion of the first solution in the third fracturing fluid is higher than that of the second solution, and the volume proportion of the first solution in the third fracturing fluid is lower than that in the second fracturing fluid.

[0070] The construction displacement continues to increase gradually. When the construction displacement value reaches the second displacement threshold (2.0m 3 / min), the fourth fracturing fluid is pumped into the wellbore to replace the third fracturing fluid, and the volume proportion of the first solution in the fourth fracturing fluid is lower than that of the second solution.

[0071] The construction displacement gradually increases, and when the construction displacement value reaches the third displacement threshold (3.0m 3 / min), a fifth fracturing fluid is pumped into the wellbore to replace the fourth fracturing fluid, and the diameter of the proppant in the fifth fracturing fluid is within a first preset diameter range; the first preset diameter range can be 30 / 50 mesh, and the volume proportion of the first solution in the fifth fracturing fluid is lower than that of the second solution; and the volume proportion of the first solution in the fifth fracturing fluid is lower than that in the fourth fracturing fluid.

[0072] The construction displacement gradually increases, and when the construction displacement value reaches the fourth displacement threshold (4.0m 3 / min), a sixth fracturing fluid is pumped into the wellbore to replace the fifth fracturing fluid, and the diameter of the proppant in the sixth fracturing fluid is within a second preset diameter range; the second preset diameter range can be 40 / 70 mesh, the volume proportion of the first solution in the sixth fracturing fluid is lower than that of the second solution; and the volume proportion of the first solution in the sixth fracturing fluid is lower than that in the fifth fracturing fluid; the sand-to-liquid ratio in the sixth fracturing fluid is higher than the sand-to-liquid ratio in the fifth fracturing fluid, and the sand-to-liquid ratio is the volume ratio of the proppant to the liquid in the fracturing fluid.

[0073] The construction displacement gradually increases, and when the construction displacement value reaches the fifth displacement threshold (5.0m 3 / min), a seventh fracturing fluid is pumped into the wellbore to replace the sixth fracturing fluid, the seventh fracturing fluid consisting of the second solution and a proppant within a third preset diameter range; the diameter of the proppant in the seventh fracturing fluid is within the third preset diameter range; the third preset diameter range can be 70 / 140 mesh, and the sand-to-liquid ratio in the seventh fracturing fluid is higher than the sand-to-liquid ratio in the sixth fracturing fluid.

[0074] In some optional embodiments, the proppant is ceramsite, and the volume ratio of the first solution to the second solution in the first fracturing fluid is nine to one, that is, 90v% of the first solution and 10v% of the second solution are mixed to obtain the first fracturing fluid.

[0075] The volume ratio of the first solution to the second solution in the second fracturing fluid is eight to two, that is, 80 v % of the first solution and 20 v % of the second solution are mixed to obtain the second fracturing fluid.

[0076] The volume ratio of the first solution to the second solution in the third fracturing fluid is six to four, that is, 60v% of the first solution and 40v% of the second solution are mixed to obtain the third fracturing fluid.

[0077] The volume ratio of the first solution to the second solution in the fourth fracturing fluid is four to six, that is, 40v% of the first solution and 60v% of the second solution are mixed to obtain the fourth fracturing fluid.

[0078] The volume ratio of the first solution to the second solution in the fifth fracturing fluid is 2 to 8; the sand-liquid ratio of the fifth fracturing fluid is 10%, that is, 20v% of the first solution and 80v% of the second solution are mixed, and 30 / 50 mesh high-strength ceramsite is added as a proppant to obtain the fifth fracturing fluid.

[0079] The volume ratio of the first solution to the second solution in the sixth fracturing fluid is 1:9; the sand-liquid ratio of the sixth fracturing fluid is 15%, that is, 10v% of the first solution and 90v% of the second solution are mixed, and 40 / 70 mesh high-strength ceramsite is added as a proppant to obtain the sixth fracturing fluid.

[0080] The seventh fracturing fluid has a sand-to-liquid ratio of 20%, that is, 100v% of the second solution is mixed, and 70 / 140 mesh high-strength ceramsite is added as a proppant to obtain the seventh fracturing fluid.

[0081] The following is an illustrative example of a method for reducing friction and compound weighting of a fracturing process:

[0082] Step 1: Taking the ultra-deep well KS-11 in western China as an example, the specific implementation method of the present invention is described. The well is a vertical well with a vertical depth of 7700m in the reformed section. According to the reservoir assessment before fracturing, the well has a high ground stress gradient, a high predicted construction pressure, and high displacement construction difficulty. In order to increase the production of a single well after reforming, a large-scale sand fracturing reformation is required. At the same time, in order to ensure construction safety, a high-density (density 1.5g / cm3) weighted fracturing fluid of 2000m3 is designed, and the designed sand addition volume is 320m3. 3. According to the technical method of the present invention, 400m3 of weighted fracturing fluid A with a density of 1.5g / cm3 is first prepared using soluble inorganic salts (bromine salts). Then, the components of 1600m3 of weighted fracturing fluid B with a density of 1.5g / cm3 are prepared. Since liquid B accounts for a high proportion during high-displacement phases, the prepared fracturing fluid is composed of approximately 74% of liquid B, thereby maximizing the proportion of low-friction liquid at high displacements and further facilitating friction reduction during high-displacement operations. Fluid B comprises 1000m3 of gel fracturing fluid base fluid, 10 tons of crosslinking agent, and 500m3 of high-strength spherical solid particles with a particle size of 200 mesh. Fracturing fluid B consists of gel fracturing fluid base fluid, 5% (weakly crosslinked) to 10% (crosslinked gel) crosslinking agent, and 60m% 200-mesh spherical solid particles. After construction begins, it is mixed in the mixing tank of a sand mixer and directly pumped. After preparing the above liquids, 50m3 of a mixed liquid of 90v% fracturing fluid A + 10v% fracturing fluid B (the volume of the tubing from the wellhead to the reformed section) is pumped in through the oil pipe at a displacement of 0.5m3 / min. In this stage, 0.5% cross-linking agent is pumped into the mixed liquid to put the mixed liquid in a weakly cross-linked state to ensure that the 200-mesh spherical solid particles do not settle.

[0083] Step 2: Pump the sealing balls at a construction displacement of 0.5m3 / min. The liquid type is 90v% inorganic salt weighted fracturing fluid A + 10v% solid phase weighted fracturing fluid B. After pumping 20m3, replace it with 80v% inorganic salt weighted fracturing fluid A + 20v% solid phase weighted fracturing fluid B. Pumping about 20m3 of the sealing balls will reach the position of the packer ball seat. After the seal is set, the displacement is increased to 1.0m3 / min. The liquid in the wellbore is gradually all 80v% inorganic salt weighted fracturing fluid A + 20v% solid phase weighted fracturing fluid B. The cross-linking agent pumped in this stage is all 1.0% in dosage to ensure that the wellbore is in a frozen gel state. The total liquid pumped in this stage is about 60m3.

[0084] Step 3: As described in the previous steps, after the operation flow rate is increased to 1.0m3 / min, the pumping liquid is adjusted to 60v% inorganic salt-weighted fracturing fluid A + 40v% solid-phase weighted fracturing fluid B, and the matching pumping crosslinker dosage is 1%. After pumping a total of 50m3 of liquid, the liquid in the wellbore is entirely 60v% inorganic salt-weighted fracturing fluid A + 40v% solid-phase weighted fracturing fluid B. Then, the operation flow rate is increased to 2.0m3 / min, and then continuously pumped 50m3. The crosslinker dosage in this stage is pumped at a ratio of 1%. The total amount of liquid used in this step is about 100m3.

[0085] Step 4: After completing step 3, increase the construction displacement to 3.0m3 / min. At the same time, the liquid is replaced with 40v% inorganic salt-weighted fracturing fluid A + 60v% solid-phase-weighted fracturing fluid B. The crosslinker pumping ratio is 1%. After 20 minutes of pumping, the pumped liquid volume is about 60m3. The liquid in the wellbore is completely replaced with 40v% inorganic salt-weighted fracturing fluid A + 60v% solid-phase-weighted fracturing fluid B. Then, at a construction displacement of 3.0m3 / min, start adding proppant, adding a sand-liquid ratio of 10%. At this construction displacement and sand-liquid ratio, the construction is carried out for 50 minutes, the construction liquid volume is 150 minutes, and the sand added is 15m3. The total construction liquid volume in this step is 210m3, and the sand added is 15m3.

[0086] Step 5. After completing step 4, increase the construction displacement to 4.0m3 / min, replace the pumped liquid with 20v% inorganic salt weighted fracturing fluid A + 80v% solid phase weighted fracturing fluid B, the cross-linking agent pumping ratio is still 1%, the entire liquid is in a cross-linked gel state, the sand-liquid ratio is increased to 15%, the total pumped liquid volume in this stage is 600m3, and the sand added volume is 90m3.

[0087] Step 6. After completing step 5, the construction displacement is increased to 5.0m3 / min, and the pumped liquid is replaced with 10v% inorganic salt weighted fracturing fluid A + 90v% solid phase weighted fracturing fluid B. The cross-linking agent pumping ratio is still 1%, the entire liquid is in a cross-linked gel state, and the sand-liquid ratio is increased to 20%. The total pumped liquid volume in this stage is 800m3 and the sand added volume is 160m3.

[0088] Step 7: After completing Step 6, the construction displacement is increased to 6.0 m³ / min. The pumped liquid is replaced with a 100% solids-weighted fracturing fluid B. The crosslinker injection ratio remains at 1%, and the entire liquid is in a crosslinked gel state. The sand-to-liquid ratio is increased to 25%. The total pumped liquid volume in this stage is 200 m³, and the added sand volume is 50 m³. The construction displacement in this step is adjusted according to the construction pressure. For ultra-deep well reconstruction using a 140 MPa wellhead, the construction displacement can be increased as much as possible under a pressure limit of 120 MPa. However, the total liquid and sand volumes in this step are controlled within the design range. This completes the well construction, with a total liquid volume of approximately 2000 m³, an added sand volume of 315 m³, and an average sand-to-liquid ratio of 15.75%. The total amount of liquid A used is 400 m³, and the amount of liquid B used is 1600 m³.

[0089] The embodiment of the present invention brings into play the respective advantages of different weighting liquids by selecting different weighting liquids at high and low construction displacements: soluble salt weighting liquid is used at low construction displacement to achieve reservoir pressure opening while reducing the risk of sand plugging (solid phase weighting). Since the absolute total friction resistance of the liquid is low at low construction displacement, the wellhead construction pressure will not be significantly increased; after increasing the construction displacement, the proportion of solid phase weighting liquid is gradually increased to maintain a relatively high net pressure of the liquid in the wellbore. At the same time, the friction resistance is not significantly increased at high construction displacement. Since the absolute liquid friction resistance along the process increased by liquid weighting does not exceed the net pressure of the liquid column increased by liquid weighting, the role of liquid weighting in reducing construction pressure is brought into play.

[0090] refer to Figure 2 As shown, Figure 2 Indicates the data corresponding to each step in the process from step 1 to step 7 above, where the blue line represents the construction displacement value corresponding to each step, and the black line represents the sand-liquid ratio value corresponding to each step. Figure 2 As can be seen from the figure, no ceramsite was added in step 1 to step 3, so the sand-liquid ratio is 0. The red line represents the real-time data of the wellhead pressure. Figure 2 It can be seen from the figure that during the process of step 1 to step 3, as the construction displacement increases, the wellhead pressure increases significantly. After the completion of step 7, the wellhead pressure decreases significantly.

[0091] Unless otherwise specifically stated, terms such as process, calculate, compute, determine, display, and the like may refer to the actions and / or processes of one or more processing or computing systems, or similar devices, that manipulate and convert data represented as physical (e.g., electronic) quantities within registers or memories of a processing system into other data similarly represented as physical quantities within the memories, registers, or other such information storage, transmission, or display devices of the processing system. Information and signals may be represented using any of a variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof.

[0092] It should be understood that the specific order or hierarchy of steps in the disclosed processes is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of the present disclosure. The accompanying method claims present elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0093] In the foregoing detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that embodiments of the claimed subject matter require more features than are expressly recited in each claim. On the contrary, as reflected in the appended claims, the invention comprises less than all the features of any individual disclosed embodiment. The appended claims are therefore hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0094] The foregoing description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purposes of describing the above embodiments, but one of ordinary skill in the art will recognize that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to encompass all such changes, modifications and variations that fall within the scope of the appended claims. Furthermore, to the extent the term "comprising" is used in the specification or claims, the term is intended to be encompassed in a manner similar to the term "including," as explained in terms of "including," used as a transitional word in the claims. Furthermore, any use of the term "or" in the specification of the claims is intended to mean a "non-exclusive or."

Claims

1. A fracturing method for reducing friction and compound aggravation, characterized in that: include: Real-time acquisition of the operation displacement value during the fracturing process; When the construction displacement value is within the initial displacement range, pumping a first fracturing fluid, wherein the first fracturing fluid comprises a first solution and a second solution in a first preset volume ratio; the first solution is a soluble inorganic salt solution, and the second solution is a solid phase fracturing fluid; After the packer is set and the operation displacement value is less than the first displacement threshold, pumping a second fracturing fluid, wherein the second fracturing fluid includes the first solution and the second solution in a second preset volume ratio; When the construction displacement value reaches the first displacement threshold, pumping a third fracturing fluid, wherein the third fracturing fluid includes the first solution and the second solution in a third preset volume ratio; When the construction displacement value reaches a second displacement threshold, pumping a fourth fracturing fluid, wherein the fourth fracturing fluid includes the first solution and the second solution in a fourth preset volume ratio; When the construction displacement value reaches a third displacement threshold, pumping a fifth fracturing fluid, wherein the fifth fracturing fluid comprises a proppant and a fifth preset volume ratio of the first solution to the second solution; When the construction displacement value reaches a fourth displacement threshold, pumping a sixth fracturing fluid, wherein the sixth fracturing fluid comprises a proppant and a sixth preset volume ratio of the first solution to the second solution; When the construction displacement value reaches a fifth displacement threshold, pumping a seventh fracturing fluid, wherein the seventh fracturing fluid includes the second solution and a proppant; The initial displacement range, the first displacement threshold, the second displacement threshold, the third displacement threshold, the fourth displacement threshold, and the fifth displacement threshold increase in sequence.

2. The method according to claim 1, wherein The volume proportion of the first solution in the first fracturing fluid is higher than that of the second solution.

3. The method according to claim 2, wherein The volume proportion of the first solution in the second fracturing fluid is higher than that of the second solution, and the volume proportion of the first solution in the second fracturing fluid is lower than that in the first fracturing fluid.

4. The method according to claim 3, wherein The volume proportion of the first solution in the third fracturing fluid is higher than that of the second solution, and the volume proportion of the first solution in the third fracturing fluid is lower than that in the second fracturing fluid.

5. The method according to claim 4, wherein The volume proportion of the first solution in the fourth fracturing fluid is lower than that of the second solution.

6. The method according to claim 5, wherein The diameter of the proppant in the fifth fracturing fluid is within a first preset diameter range; The volume proportion of the first solution in the fifth fracturing fluid is lower than that of the second solution; and the volume proportion of the first solution in the fifth fracturing fluid is lower than that in the fourth fracturing fluid.

7. The method according to claim 6, wherein The diameter of the proppant in the sixth fracturing fluid is within a second preset diameter range; The volume proportion of the first solution in the sixth fracturing fluid is lower than that of the second solution; and the volume proportion of the first solution in the sixth fracturing fluid is lower than that in the fifth fracturing fluid; The sand-to-liquid ratio in the sixth fracturing fluid is higher than the sand-to-liquid ratio in the fifth fracturing fluid, where the sand-to-liquid ratio is the volume ratio of proppant to liquid in the fracturing fluid.

8. The method according to claim 7, wherein The seventh fracturing fluid is composed of the second solution and a proppant with a third preset diameter range; the diameter of the proppant in the seventh fracturing fluid is within the third preset diameter range; The sand-to-liquid ratio in the seventh fracturing fluid is higher than the sand-to-liquid ratio in the sixth fracturing fluid.

9. The method according to claim 1, wherein The density of the first solution is 1.5 g / cm 3 .

10. The method according to claim 1, wherein The second solution includes solid spherical particles and jelly fracturing fluid; The density of the second solution is the same as that of the first solution.

11. The method according to claim 10, wherein The particle size of the solid spherical particles is 200 mesh, and the solid spherical particles are insoluble.

12. The method according to claim 1, wherein The volume ratio of the first solution to the second solution in the first fracturing fluid is nine to one; The volume ratio of the first solution to the second solution in the second fracturing fluid is eight to two; The volume ratio of the first solution to the second solution in the third fracturing fluid is six to four; The volume ratio of the first solution to the second solution in the fourth fracturing fluid is four to six; The volume ratio of the first solution to the second solution in the fifth fracturing fluid is 2 to 8; the sand-to-liquid ratio of the fifth fracturing fluid is 10%; The volume ratio of the first solution to the second solution in the sixth fracturing fluid is 1:9; the sand-to-liquid ratio of the sixth fracturing fluid is 15%; The sand-to-liquid ratio of the seventh fracturing fluid is 20%.

13. The method according to claim 1, wherein The proppant is ceramsite.

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