Laboratory Evaluation of Thermoreversible Gel for In-Depth Conformance Control in Steam-Stimulated Wells

摘要

Cyclic steam stimulation(CSS) is one of the most common methods used to improve oil recovery in heavy oil reservoirs. However, due to reservoir heterogeneity, unfavorable mobility ratio and gravity segregation, steam channeling through high permeability zones occurs, resulting in poor sweep efficiency and a reduction in ultimate oil recovery. To settle the steam channeling problem, this paper presents the laboratory evaluation of a thermoreversible gel formed from hydroxypropyl methylcellulose (HPMC) for in-depth conformance control in steam-stimulated well. The effects of concentration of HPMC, sodium chloride and urea on the gelation temperature, gel strength and degree of syneresis observed in gel samples were studied. The long-term thermal stability of the thermoreversible gel was evaluated. Sandpack flow experiments were conducted to evaluate the reversibility of plugging and selective plugging ability. The experimental results showed that as the concentration of HPMC increased, the gelation temperature, degree of syneresis decreased and gel strength increased. Based on proper gelation temperature, good gel strength, degree of syneresis and economical cost, the proper concentration of HPMC should range from 2.0wt% to 2.5wt%. The gelation temperature and gel strength increased with increasing sodium chloride concentration. While as urea concentration increased, the gelation temperature increased and gel strength decreased. After aging for 60days at 110°C, about 3.5% syneresis was observed in gel samples, which indicated that the gel had good long-term thermal stability. The singular and parallel sandpack flow results showed that the thermoreversible gel had good reversibility of plugging and selective plugging ability. Therefore, these results indicate that the thermoreverible gel studied here are good candidates for in-depth conformance control in steam-stimulated wells, which can provide a basis for field application.