Volume 57

Research on the Mechanism of Gas Injection for Enhanced Production in High-Sulfur Gas Reservoirs Guixue QI

Abstract

The marine acidic gas in Zhongyuan Oilfield is mainly distributed in the Puguang gas field in northeastern Sichuan, with characteristics such as “burial permeability, high H2S and CO2 content, and strong edge and bottom water”. As the gas field development enters the middle and lat-er stages, there are problems such as continuous decrease in formation pressure, water invasion, and increasingly serious sulfur deposition. Energy supplementation effects of gas injection with flue gas, tail gas, nitrogen, and COâ‚‚. Experiments show that the production enhancement effects are comparable under different injected media; the displacement recovery efficiency of gas-displacing-gas is high, and under the condition of equal injection volume, the recovery efficiency differs by only 0.5% – 0.9%. Compared with depletion development to different abandonment pressures, gas injection can increase the recovery efficiency by 10-27 percentage points. Gas injection for energy supplementation prioritizes the production of main layers. When 0.7 PV is injected, the recovery factor basically reaches 93%. The poor layers are affected by the partial pressure and split gas volume, resulting in slow response to energy supplementation. However, their recovery factor continues to increase as the injected gas volume rises. The main mechanisms of enhanced oil recovery by gas injection in the Puguang Gas Field are energy supplementation and displacement. Capturing COâ‚‚ and reinjecting it into gas reservoirs in high-sulfur gas fields can effectively improve oil recovery, and reinjecting tail gas can reduce carbon emissions, contributing to the achievement of the “dual carbon” goals.

Keywords High-Sulfur Gas Reservoirs, Enhanced Production, Gas Injection, Mechanism Research