一种考虑滤失的水平裂缝延伸新模型

为满足工程设计的需要,以缝中流体单元的受力分析为基础,综合流体力学理论、弹性力学理论和物质平衡原理,重新建立了水平裂缝中压力分布、水平裂缝宽度和水平裂缝延伸半径等数学模型以及用差分法离散后的数值模型,并用牛顿迭代方法进行数值求解。这些模型综合考虑了压裂液滤失对缝中压力分布及流量分布的影响、能准确模拟水平裂缝延伸过程。研究结果表明,系统中考虑压裂液滤失对缝中流量和压力分布的影响而建立的水平裂缝延伸模型,由于考虑了水平裂缝中压裂液流量的实际分布,能准确描述水平裂缝延伸过程,模拟出的缝中流量沿裂缝半径逐渐减小至零,计算出的缝裂缝半径和缝宽均比原有模型结果小,符合水平裂缝压裂的现场实际。提出的迭代数值解法稳定可靠,其方法和思路为水平裂缝参数分析和施工设计奠定了基础。

A NEW MODEL SIMULATING HORIZONTAL FRACTURE EXTENSION WITH LEAKOFF EFFECTS

With the development of shallow reservoirs, horizontal fracture has emerged, and the research on horizontal fracture has become one of the most important aspects of hydraulic fracturing research. Many fruitful studies have been done on simulating horizontal fracture extension. But all the models neglect the effects of leakoff on the distribution of flowing rate andpressure in fracture, which significantly deviate from the practical simulation treatment. Combining the relative knowledge of hydrodynamics, elasticity mechanics and principle of material equilibrium, and based on cell mechanical analysis, this paper presents a new model simulating horizontal fracture propagation which takes the effects of leakoff on the distribution of flowingrate and pressure in fracture into account, and the numerical solution of the model by newton iteration is developed too. The calculating results show that the model and its solution are stable and reliable. Compared to the results calculated by those models neglecting the effects of leakoff, the model predicts a shorter and narrower horizontal fracture.