苏里格致密砂岩压裂中转向剂用量与转向角的关系

绒囊转向剂通过改变岩石强度控制裂缝走向，已在现场应用获得印证，但是缺乏裂缝转向理论研究。转向剂强度与转向角的关系是转向裂缝准确地延伸至预定位置的关键之一。室内进行转向剂封堵实验和岩石三轴实验，用囊层剂+1.5%绒毛剂+0.3%成核剂+0.5%成膜剂配制绒囊转向剂，测得注入量为4、8、10、12 mL时，封堵后承压达到10.15、12.37、16.52、25.14 MPa；绒囊转向剂封堵直径75 mm致密砂岩岩心人造裂缝，通过三轴试验机测得封堵前后岩心径向应力应变曲线拐点从0.004 8 mm/mm升至0.012 7 mm/mm，轴向曲线拐点从0.014 3 mm/mm升至0.018 6 mm/mm，说明岩心强度提高。测得转向角增量分别为24.9°、23.2°、37.5°和55.9°。根据4组岩心封堵后弹性模量19.55、16.65、19.61、19.77 GPa和泊松比0.36、0.30、0.46、0.38，选择影响转向角度的参数为弹性模量和泊松比，用最小二乘法方法拟合参数与裂缝转向角度之间的数学关系，得到弹性模量与泊松比商的自然对数与转向角度呈线性关系，进而得到注入量与转向角的函数关系。结果表明，绒囊流体的注入量可以控制转向角度，进而实现转向裂缝准确延伸至目的层位。 

Functional Relationship between Amount of Diverting Agent and Diverting Angle in Fracturing Tight Sandstones in Sulige Gas Field

Field practices have proved that fuzzy ball diverting agent is able to control fracture strike by altering rock strengths, theoretical study on diversion of fractures is rarely seen though. The relationship between the strength of diverting agent and diverting angle is one the key factors that ensures the diverted fractures extend to the designed positions. Diverting agent plugging experiment and rock triaxial stress experiment were done on a fuzzy ball diverting agent formulation:2.0% epithecium agent+1.5% fuzz agent + 0.3% nucleating agent+0.5% filming agent. When injecting 4, 8, 10 and 12 mL fuzzy ball diverting agent, the pressure bearing capacity of the formation being plugged by the diverting agent was 10.15 MPa,12.37 MPa,16.52 MPa and 25.14 MPa, respectively. An artificial sandstone core of 75 mm in diameter was tested on triaxial stress tester before and after being plugged with the fuzzy ball diverting agent, an inflexion point was found on the radial stress-strain curve at which the strain increased from 0.0048 mm/mm to 0.0127 mm/mm. On axial stress-strain curve there was also an inflexion point at which the strain increased from 0.0143 mm/mm to 0.0186 mm/mm. These data indicate that rock strength was increased. In calculating elastic modulus by dividing stress by axial strain, and Poisson ratio by dividing transversal strain by axial strain, in was found that the incremental diverting angles measured were 24.9°, 23.2°, 37.5°, and 55.9°, respectively. Four rocks after being plugged had elastic modulus of 19.55 GPa, 16.65 GPa, 19.61 GPa and 19.77 GPa, respectively, and Poisson ratios of 0.36, 0.30, 0.46 and 0.38, respectively. Using elastic modulus and Poisson ratio as the parameters affecting diverting angle, fit the mathematical relationship between the parameters and the diverting angle of fractures with least square method. It was found that the natural logarithm of the quotient of elastic modulus/Poisson ratio was linearly related to the diverting angle. From this finding a functional relationship between injection amount of diverting agent with diverting agent has been worked out. It is understood that the injection amount of the fuzzy ball fracturing fluid is able to control the diverting angle, thereby extending the diverted fractures to the target zones.