摘要：Radial drilling-fracturing, the integration of radial drilling and hydraulic fracturing, is an innovative approach to develop low permeability, thin target layer and naturally fractured reservoirs, etc. Understanding the fracture initiation process is required in the practical application to avoid high fracture initiation pressure (FIP) and complex fracture geometries near the wellbore. In this paper, we develop an analytical model to determine FIP, location of rock failure zones and initial fracture direction from the radial lateral borehole. This model is based on the stress superposition induced by cased main wellbore and radial borehole, and the maximum tensile stress criterion is adopted. Then, we perform a series of sensitivity analysis by examining different effects of in-situ stress regime, lateral orientation (the included angle between borehole axis and maximum horizontal in-situ stress), lateral length, and lateral diameter. Besides, the effect of pre-existing weakness plane, across which the tensile strength is much lower than that of the intact rock, is also investigated, when the plane is drilled through by the radial borehole. Results show that for intact rock with no weakness plane, the in-situ stress regime and lateral orientation are main factors influencing FIP, location of rock failure zones, and initial fracture direction. Under the in-situ stress regime of normal fault, fracture initiates vertically, and FIP enlarges as lateral orientation increasing; under the in-situ stress regime of strike slip, fracture initiates vertically with small lateral orientation, while fracture initiates horizontally with large lateral orientation; and under the in-situ stress regime of reverse fault, fracture initiates horizontally with any lateral orientation, and FIP decreases as the lateral orientation increasing. It is also found that when the fracture initiates vertically, the location of rock failure zones is at the base of radial borehole on its top and bottom sides; and when the fracture initiates horizontally, the location of rock failure zone is at the remote region of radial borehole on its right and left sides. The lateral length has a minor effect on fracture initiation, and the influence of lateral diameter is negligible. When the weakness plane is drilled through by the radial borehole, fracture initiation pressure from weakness plane is affected by its occurrence, i.e., azimuth and inclination. FIP is determined by taking the minimum between fracture initiation pressure from rock matrix and the weakness plane. The key findings of this work could provide critical insights into understanding radial drilling-fracturing initiation characteristics.
© 2018 Elsevier B.V.

ISSN号：0920-4105

卷、期、页：v 164,p206-218

发表日期：2018-05-01

期刊分区（SCI为中科院分区）：三区

收录情况：SCI（科学引文索引印刷版）,ESI（基本科学指标数据库）,EI（工程索引）,SCIE（科学引文索引网络版）

发表期刊名称：JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING

通讯作者：刘庆岭,李小江,王天宇

第一作者：田守嶒,李根生,盛茂,沈忠厚

论文类型：期刊论文

论文概要：刘庆岭,田守嶒,李根生,盛茂,李小江,王天宇,沈忠厚，An analytical model for fracture initiation from radial lateral borehole，JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING，2018，v 164,p206-218

论文题目：An analytical model for fracture initiation from radial lateral borehole