Simulation on Heavy Oil Production With In-Situ Combustion in the Northern Oilfield of Thailand

Abstract

An oilfield in the North of Thailand has medium viscous heavy oil. Since the normal production methods are ineffective, thermal recovery is suitable to enhance oil recovery. In-situ combustion is a complex EOR process used for this crude oil. Recovery mechanisms include viscosity reduction from heating, fluid vaporization and thermal cracking. However, a major problem is the control of the movement of the combustion front. Depending on the reservoir and fluid characteristics, the combustion front may move in a non-uniform way, with resulting poor performance. The parameters such as injection rates, oxygen concentration, and air temperature play a significant role for in-situ combustion process because they can control the sustainability of the front. Therefore, the objectives of this work are to investigate the effects of parameters on the production of heavy oil, to predict the behavior of the combustion front and to assess the optimal conditions to enhance the efficiency of heavy oil production by using simulation with the real data of the oilfield in Thailand. For this study, CMG program is used to set up and simulate the model. The formation of this oilfield is sandstone with average 500 md permeability, 18-35% porosity and 53.7 cP viscosity. The results are investigated by conducting a number of sensitivity studies with various parameters. The results show that changing injection rate from 100 Mscf/d to 400 Mscf/d has less effect on cumulative oil production which is less than 6% incremental recovery. However, an increase in oxygen concentration from 29% to 100% can enhance oil production for 40.67%. Moreover, if the injected fluid temperature is increased from 80 ○F to 500 ○F, total oil production increases up to 97.14%. In addition, the optimal operating conditions are adjusted to enhance recovery of oil production. A decrease in injection rate from 100 Mscf/d to 50 Mscf/d after ignition is selected. High injected fluid temperature is required to reduce ignition time. However, it is not necessary to maintain high temperature at all time. Injected fluid temperature is reduced from 300 ○F to 80 ○F after ignition has started. Moreover, oxygen concentration is the key of combustion process in that the smaller number of oxygen molecule reacts, the lower heat will be released. The results of this study can be applied as a fundamental data for in-situ combustion project development in the heavy oilfield in the North of Thailand in the future.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018