Reservoir characteristics and effective development technology in typical low-permeability to ultralow-permeability reservoirs of China National Petroleum Corporation

Xizhe Li,Shujun Li,Zhengming Yang,Wei Lin,Wei Huang,Jianfei Zhan

doi:10.1177/01445987211005212

Abstract

Low-permeability to ultralow-permeability reservoirs of the China National Petroleum Corporation are crucial to increase the reserve volumes and the production of crude oil in the present and future times. This study aimed to address the two major technical bottlenecks faced by the low-permeability to ultralow-permeability reservoirs by a comprehensive use of technologies and methods such as rate-controlled mercury injection, nuclear magnetic resonance, conventional logging, physical simulation, numerical simulation, and field practices. The reservoir characteristics of low-permeability to ultralow-permeability reservoirs were first analyzed. The water flooding development adjustment mode in the middle and high water-cut stages for the low-permeability to ultralow-permeability reservoirs, where water is injected along the fracture zone and lateral displacement were established. The formation mechanism and distribution principles of dynamic fractures, residual oil description, and expanding sweep volume were studied. The development mode for Type II ultralow-permeability reservoirs with a combination of horizontal well and volume fracturing was determined; this led to a significant improvement in the initial stages of single-well production. The volume fracturing core theory and optimization design, horizontal well trajectory optimization adjustment, horizontal well injection-production well pattern optimization, and horizontal well staged fracturing suitable for reservoirs with different characteristics were developed. This understanding of the reservoir characteristics and the breakthrough of key technologies for effective development will substantially support the oil-gas valent weight of the Changqing Oilfield to exceed 50 million tons per year, the stable production of the Daqing Oilfield with 40 million tons per year (oil-gas valent weight), and the realization of 20 million tons per year (oil-gas valent weight) in the Xinjiang Oilfield.

Highlights

Low-permeability to ultralow-permeability reservoirs have significant development potential
According to data collected in 2006, the China National Petroleum Corporation (CNPC)’s annual proven low-permeability reserves contain 430 million tons of crude oil, accounting for 71.8% of China’s annual proven low-permeability reserves
The physical properties and reservoir distribution characteristics of typical lowpermeability to ultralow-permeability reservoirs of CNPC were compared, and the factors that affect the yield of the ultralow-permeability reservoirs were unraveled

Summary

Introduction

Low-permeability to ultralow-permeability reservoirs have significant development potential. The Changqing Oilfield is a block reservoir with massive sand bodies; the Daqing Oilfield is a multi-layer reservoir with thin and narrow sand bodies, and the Xinjiang Oilfield is a conglomerate reservoir (Wang et al, 2008a, 2008b; Zeng, 2004; Zeng et al, 2008). These lowpermeability to ultralow-permeability reservoirs face two major technical bottlenecks. The second challenge in exploitation of the reserves is that the ultralow-permeability reservoirs have fine pore throats, because of which it is difficult to develop an effective displacement system, and the degree of reserve utilization is low (Du et al, 2014; Gan et al, 2011; Li et al, 2015; 2019; Lin et al, 2020; Shen et al, 2016, 2019; Su and Sun,1996; Yang et al, 2010; Zeng et al, 2010)

Objectives

Findings

Conclusion