Xinjiang Petroleum Geology ›› 2023, Vol. 44 ›› Issue (5): 583-591.doi: 10.7657/XJPG20230510

• RESERVOIR ENGINEERING • Previous Articles     Next Articles

Water Invasion Characteristics and Residual Gas Distribution in Fractured-Porous Carbonate Reservoirs

XIE Peng1(), CHEN Pengyu2, ZHAO Hailong3, Xu Jianting4   

  1. 1. International Engineering Company, Chuanqing Drilling Engineering Co., Ltd., CNPC, Chengdu, Sichuan 610000, China
    2. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
    3. School of Petroleum Engineering, China University of Petroleum, Qingdao, Shandong 266580, China
    4. PetroChina Amu Darya Gas Exploration and Development (Beijing) Co., Ltd., Beijing 100034,China
  • Received:2022-12-05 Revised:2023-03-17 Online:2023-10-01 Published:2023-09-25

Abstract:

Water channeling often occurs in gas wells during the production of fractured-porous carbonate gas reservoirs with edge/bottom water. A simulation experiment on water invasion mechanism was performed by using a visualized microscopic model and under the formation conditions simulated by the high-temperature high-pressure online nuclear magnetic resonance detection system, to study the distribution of residual gas. The distribution of intrusive water was characterized by the T2 spectrum obtained from pulse sequence testing. The results show that the pore-throat ratio, coordination number, and fracture width have significant impacts on water invasion and residual gas distribution. In porous reservoirs, invasion water first enters large pores and then small pores. In fractured-porous reservoirs, where the distribution of fractures has an influence on the water invasion mode, intrusive water enters the fractures and then the medium-large pores. In water-invaded porous reservoirs, 37.7% of the residual gas exists in small pores, and 62.3% in large pores. In water-invaded fractured-porous reservoirs, a little residual gas is in fractures, 4.8%-26.8% of the residual gas in small pores (where the residual gas is difficult to recover), and 94.7%-69.2% in medium-large pores. The residual gas saturation index was evaluated with the water invasion proportion in medium-large pores as an objective function, and the main controlling factors include fracture penetration degree, water volume ratio, fracture width and gas production rate. The well trajectory should be optimized in the fracture zones and kept away from the fractures that communicate with edge/bottom water. Furthermore, well production rate should be optimized to delay water breakthrough. After water breakthrough in gas wells, the gas production rate should be appropriately reduced to drive intrusive water into medium-large pores and reduce residual gas in the medium-large pores, thus enhancing the gas recovery.

Key words: carbonate rock, gas reservoir, fractured-porous reservoir, nuclear magnetic resonance, water invasion characteristic, residual gas distribution, gas production rate, EOR

CLC Number: