Bai Mingxing, Zhang Zhichao, Chen Qiaozhen, Weifeng Shao, Du Siyu
School of Petroleum Engineering, Northeast Petroleum University, 163318 Daqing, Heilongjiang Province, China.
Mechanical and Electrical Information Engineering College, Daqing Normal University, 163318 Daqing, Heilongjiang Province, China.
ACS Omega. 2021 Oct 19;6(43):28485-28495. doi: 10.1021/acsomega.1c00893. eCollection 2021 Nov 2.
The low oil productivity of tight oil reservoirs is mainly caused by poor reservoir physical properties such as low porosity and permeability, a small pore and throat ratio, and bad well connectivity, which lead to bad water injection capability and rapid pressure decline for the reservoir. In this paper, an enhanced oil recovery technique for tight oil reservoirs is proposed by combination of horizontal well volume fracturing and CO huff-n-puff to improve the reservoir physical properties and increase the flow capability of crude oil. In the initial reservoir development stage, the precise horizontal well trajectory and reservoir volume fracturing scale are designed by analyzing the distribution of sand body thickness and the oily sedimentary facies. The micro-seismic tracking technique is also used to monitor the fracture elongation. When the reservoir energy cannot satisfy the economic limit of oil productivity, the CO huff-n-puff technique is applied to increase the reservoir energy quickly. After the precise fracturing technique is used in tight oil Block X, the average oil production rate of six fractured horizontal wells increases by 5 ton (1 ton = 7.33 bbl) at the initial production stage, and the effective oil production increase life lasts for 32 months. When the reservoir energy is supplemented using the CO huff-n-puff technique, the oil production rate of pilot experiment well SP-1 increases from 1.9 to 12.8 ton with a cumulative oil increase of 1333.8 ton.
致密油藏原油产能低主要是由于储层物性差，如孔隙度和渗透率低、孔喉比小以及井间连通性差，这些导致注水能力差且储层压力快速下降。本文提出了一种将水平井体积压裂与CO2吞吐相结合的致密油藏提高采收率技术，以改善储层物性并提高原油流动能力。在油藏开发初期，通过分析砂体厚度分布和油层沉积相来设计精确的水平井轨迹和储层体积压裂规模。还使用微地震跟踪技术来监测裂缝延伸情况。当油藏能量不能满足原油产能的经济极限时，应用CO2吞吐技术快速提高油藏能量。在致密油X区块应用精确压裂技术后，6口压裂水平井在投产初期平均日产油量增加5吨（1吨 = 7.33桶），有效增产持续时间达32个月。当采用CO2吞吐技术补充油藏能量时，试验井SP - 1的产油量从1.9吨增至12.8吨，累计增油1333.8吨。
