Li Ting, Tan Yongsheng, Dai Shuhui, Zhou Xun, Yu Jinzhu, Yang Qi
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China.
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China.
ACS Omega. 2020 Dec 29;6(1):615-622. doi: 10.1021/acsomega.0c05119. eCollection 2021 Jan 12.
Fracturing measures are common practice for horizontal wells of tight oil reservoirs. Thus, production estimation is a significant problem that should be solved. However, previous models for the production of fractured horizontal wells of tight oil reservoirs have some problems. In this paper, we present a semi-analytical model based on the volumetric source method to simulate production from nonplanar fracture geometry in a tight oil reservoir. First, we developed an analytical model based on the volumetric source method in nonplanar fracture geometry with varying widths. Second, the model was coupled with fracture flow and solved by the Gauss-Seidel iteration. Third, the semi-analytical model was verified by a numerical reservoir simulator. Finally, sensitivity analysis was conducted for several critical parameters. Results of validations showed good agreement between this paper's model and the numerical reservoir simulator. The results from the sensitivity analysis showed that (1) production increases with an increased number of fracture segments; (2) production drops more quickly with a smaller fracture half-length in the first stage, and it drops slowly with a smaller fracture half-length in the second stage; (3) cumulative production increases more quickly with a bigger fracture conductivity; and (4) cumulative oil production from a fracture with a constant width and without stress sensitivity coefficient is smaller than that from a fracture with varying widths and with stress sensitivity coefficient. This research provides a basis and reference for production estimation in tight oil reservoirs.
压裂措施是致密油藏水平井的常用做法。因此，产量预测是一个需要解决的重要问题。然而，以往致密油藏压裂水平井产量模型存在一些问题。本文提出一种基于体积源法的半解析模型，用于模拟致密油藏非平面裂缝几何形状的产量。首先，基于体积源法建立了非平面裂缝几何形状、宽度变化的解析模型。其次，将该模型与裂缝流动耦合，采用高斯 - 赛德尔迭代法求解。第三，用数值油藏模拟器对该半解析模型进行了验证。最后，对几个关键参数进行了敏感性分析。验证结果表明本文模型与数值油藏模拟器结果吻合良好。敏感性分析结果表明：（1）产量随裂缝段数增加而增加；（2）在第一阶段，裂缝半长越小产量下降越快，在第二阶段，裂缝半长越小产量下降越慢；（3）累积产量随裂缝导流能力增大而增加更快；（4）宽度不变且无应力敏感系数的裂缝累积产油量小于宽度变化且有应力敏感系数的裂缝累积产油量。该研究为致密油藏产量预测提供了依据和参考。
