Field Pilots Show Effectiveness of Foams in Low-Porosity Naturally Fractured Reservoir

Abstract

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper IPTC 17950, “Foams Prove Effectiveness for Gas-Injection Conformance and Sweep-Efficiency Improvement in a Low-Porosity Fractured Reservoir—Field Pilots,” by A. Ocampo, SPE, A. Restrepo, N. Rendon, J. Coronado, J. Correa, D. Ramirez, M. Torres, and R. Sanabria, Equion Energia, and S. Lopera, National University of Colombia, prepared for the 2014 International Petroleum Technology Conference, Kuala Lumpur, 10–12 December. The paper has not been peer reviewed. Foams have proved to be efficient at temporarily blocking high-conductivity layers and improving gas-injection conformance and sweep efficiency in predominantly matrix reservoir systems, at least in laboratory and field pilot tests. However, their successful use in naturally fractured reservoirs has yet to be fully demonstrated. This paper presents the evaluation process and the successful results for two foam-enhanced-oil-recovery (EOR) field pilots. Introduction The Recetor area corresponds to the northern extension of the larger Cupiagua field, which is 115 km northeast of BogotÁ in the foothills of the Eastern Mountain chain in Colombia. The main reservoir is the Mirador formation, a quartzarenite with matrix porosities between 3 and 9% and permeabilities in the range of 0.01 to 10 md, located below 13,000-ft true vertical depth subsea. In the Recetor area, the fracture corridors are confirmed to play an important role both in well productivity/ injectivity and in interwell connectivity and gas channeling between gas injectors and oil producers. This is confirmed by the high connectivity between most of the wells and the observed levels of gas recycling, which could not be explained by the low matrix permeabilities. Current condensate recovery factor is approximately 34%, and steep evolution of gas production has been observed in the wells influenced by the two main gas injectors (LR YR-7 and LR YZ-11) during the last 2 years, with gas/ oil ratios (GORs) ranging from 40,000 to 100,000 scf/STB. The foam-EOR pilot projects in the Mirador formation of the Recetor area were aimed at controlling, or at least mitigating, the high levels of gas recycling between the main gas injectors and their respective oil producers. They were engineered to improve both the vertical conformance of the gas at the injector wells and the sweep efficiency deep into the reservoir, by use of limited slugs of liquid foaming solutions followed by gas injection.