Tengiz Field Sector Model for IOR/EOR Process Evaluation

Abstract

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 170605, ’A Sector Model for IOR/EOR Process Evaluation,’ by Shie-Way Wang, Batima Yeskaiyr, SPE, and Chuck Walker, Tengizchevroil, prepared for the 2014 SPE Annual Technical Conference and Exhibition, Amsterdam, 27-29 October. The paper has not been peer reviewed. This work presents a methodology to construct a sector model for the Tengiz field that covers one-sixth of the field area to evaluate improved-/ enhanced-oil-recovery (IOR/EOR) processes to increase oil recovery through the life of the field. The method takes into account boundary flux, edge wells, and compositional effects to replicate full-field-model performance and subsequently generate alternative predictions. This model matches production/injection data of existing wells and the anticipated performance of future wells in the full-field model. Introduction The Tengiz field is a giant carbonate oil field onshore western Kazakhstan at the northern end of the Caspian Sea’s eastern shoreline. Tengiz is a stratigraphic trap consisting of a carbonate buildup with a large central platform area (10×15 km) with a raised rim area (up to 2 km wide). The Tengiz reservoir has mesa-like geometry overall—flat topped and steep sided. The top of the platform has a slight regional tilt (less than 1° to the south). The sides of the platform generally dip approximately 25° on all flanks. Production has been mainly from primary pressure depletion through oil expansion. Sour-gas injection was implemented in 2007 to address pressure decline and improve recovery efficiency. In general, the platform lacks fractures and is best suited for gas injection, whereas the slope is suitable for depletion drive because of high fracture density. Because gas injection is limited to the platform region, the main objective of this study is to investigate the best pressure-maintenance or IOR/EOR method to apply to the fractured slope region. Sector Model The area of the field modeled with the sector model was selected to include geological regions, material-balance regions, and displacement processes that are representative of Tengiz as a whole. The model incorporates 15.2% of the field surface area and has platform and slope regions within its boundary. Fig. 1 shows that the sector model includes (a) two five-spot existing sour-gas-injection patterns (green-line-pattern area) and (b) seven future-growth-project and sour-gas-injection patterns in the central platform region (black-line-pattern area). This sector model has 127 wells divided into two groups. The first group has 62 future and existing producers and eight injectors associated with base business operations. The second group has 57 potential future infill wells for long-term IOR/EOR development plans.