| Tight reservoir development generally requests reservoir reconstruction. The flow conductivity of major fractures and secondary fractures is the key of the producibility increase effect, so it is important to study of fracture conductivity. This paper used the Changqing HQ and Qinghai ZP tight reservoir as the study area, based on the analysis of volume fracturing net and the mechanism of crack shear slip, using laboratory test methods for major and secondary fracture conductivity and its influencing factors were studied systematically. Use the experimental data to calculate the producibility analysis of study area and verify the feasibility of experimental methods and achieved the following results and understanding:(1) Combined with the previous research of study area to describe the fracture characteristics and its distribution. The fracture characteristics is “small cut depth, small opening, small pitch”, belong to small-micro fracture system. The fracture advantage orientation is North 80°~90° West, South 60°~70° East.(2) To analyze the mechanism of shear fractures formation and slip use the mechanical method. The main factors affecting the joints fracture slip are the long of fractures, elastic modulus and stress difference and calculate the maximum capacity of up to 6 ~ 8mm displacement when the fracture length 8~10m of the study area. Use the Fractal dimension methods to calculate the rough surface and achieve the simulation of fracture face.(3)Study the conductivity under different artificial fracture state use API standards. The relationship between conductivity and closing pressure all follow the law of diminishing Index; The conductivity of rough surface displacement without prpppant is more an order of magnitude than integraded fractures; The long time conductivity of Ceramic and quartz sand all follow the law that the initial diversion of diminishing rapidly, the late fall flat characteristics.(4)Do the conductivity experiment used conventtional core with artifical fractures in Changqing and Qinghai tight reservoirs. Simulate secondary fractures in various states of volume fracturing, study the relationship between conductivity and closure stress and other factors. The closed artificial fractures and some improvement to reservoir flow, but fractures have no elastic recovery; Under the multilayer sanding, the conductivity is proportional to the fracture width; The conductivity and density consistent with the single "Single hump" shaped curve under conditions of single local sanding; Fracture displacement conductivity is closed with rough surface and lithology, the more rough surface fractal dimension, the higher conductivity; The larger the rock hardness, conductivity after displacement less affected by pressure; Fracturing fluid and liquid exists both will cause some damage.(5)The study area HQ reservoir short dimensionless conductivity between 1.2 to 1.5 and long dimensionless conductivity between 0.2~0.25; Use the Mcguire-Sikora type semi-logarithmic increase plates and dimensionless proppant number calculated times of production are respective 1.9 to 3.8 times and 1.65 to 3.66 times, this validate the feasibility of Conductivity experiments and the experimental data have some guidance to the field. |
PDF Full Text Request