Feasibility Study of Heavy oil Recovery Using In-situ Steam Generated by Thermochemicals

Abstract

Abstract Alaska North Slope (ANS) contains heavy oil (12-23 API) with an estimated range of original oil in place (OOIP) of 13 to 25 billion barrels. This resource has been considered as one of the largest heavy oil deposits in the United States. However, several technical challenges are limiting its commercial development. One of the most significant difficulty is the overlying 1,800-2,000 ft-thick permafrost layer, which causes unavoidable significant heat losses when steam is injected from the surface steam generators, and the potentially disastrous effects due to melting of the permafrost around the cemented casing. Therefore, surface steam injection might not be a viable option to develop this resource, although it is the most commonly used approach of heavy-oil recovery. Hence, the objective of this research is to conduct a feasibility study on the application of new approach, in which steam is generated downhole using thermochemical reaction (SGT) combined with steam assisted gravity drainage (SAGD), to recover heavy oil from Ugnu reservoir which is one of the major oil deposits in ANS. A numerical simulation model for Ugnu heavy oil reservoir is built using CMG-STARS simulator. Then a MATLAB framework is integrated with the simulation model to study different recovery strategies on the project profitability. Net Present Value (NPV) is used in this study as the key performance indicator while monitoring oil recovery factor (RF) and cumulative oil production (COP). The design and operational parameters studied and optimized in this paper involve; 1) well configurations and locations, 2) steam injection rate and quality, steam trap and startup heating period to initialize SAGD process. The results show that the in-situ SGT is a successful approach to recover heavy oil from Ugnu reservoir and it yields high project profitability, in terms of the NPV after 10 years of development. The main reason of this outperformance is ability of SGT to avoid the significant heat losses and associated costs, in the surface steam injection methods. This paper introduces a novel approach to generate downhole steam using thermochemical reactions to overcome the challenges associated with heavy-oil resource development from Ugnu reservoir, while minimizing the environmental impact by reducing the greenhouse gas emission related to surface steam injection methods.