Feasibility, Application and Evaluation of Dilation by Polymer Injection Technology to Improve SAGD Process

Liang, Guangyue (Research Institute of Petroleum Exploration and Development, CNPC) | Liu, Shangqi (Research Institute of Petroleum Exploration and Development, CNPC) | Liu, Yang (Research Institute of Petroleum Exploration and Development, CNPC) | Zhou, Jiuning (Research Institute of Petroleum Exploration and Development, CNPC) | Han, Bin (Research Institute of Petroleum Exploration and Development, CNPC) | Bao, Yu (Research Institute of Petroleum Exploration and Development, CNPC) | Huang, Jixin (Research Institute of Petroleum Exploration and Development, CNPC)

OnePetro 

Abstract

The preheating start-up is indispensable before converting to super heavy oil and oil sands SAGD process. It is mainly achieved through steam circulation or stimulation. Either way, the preheating time and steam consumption are usually over 5 months and 30,000 tons, respectively, especially for well pairs in reservoir with bottom transition zone or widely distributed mudstone. Thus, a modified technology about dilation by polymer injection was proposed and demonstrated to improve oil sands SAGD performance.

Based on the data of mini-fracture test, tri-axial test and core test of polymer displacement, the feasibility study of dilation by polymer injection technology to improve SAGD process was conducted. On the basis, the pilot test and follow-up steam circulation process were well-designed and history matched by coupled geomechanical and thermal simulations, considering the mechanisms of polymer adsorption, degradation reaction, shear thinning and residual resistance, etc. Specially, the key to success of dilation by polymer injection technology was also analyzed.

The feasibility study indicates that the vertical dilated zone easily creates and fast start-up process can be achieved under high injection pressure. While the reservoir is first dilated to form a high-porosity and high-permeability conduit connecting the SAGD well pair, the polymer solution is then injected into these newly created pore spaces, yielding a greater range of dilated zone which is more uniform along the horizontal section. The history matching results demonstrate that inter-well porosity and permeability significantly enhance. Compared with adjacent well pairs, thermal and hydraulic connectivity obviously improve, both steam consumption and circulation time reduce nearly by half. Besides, the first year oil rate improves in follow-up SAGD process.

The field experience and findings can help to improve the SAGD performance and economy of super heavy oil and oil sands projects, especially for heterogeneous reservoir with bottom transition zone or widely distributed mudstone.