Planning and Implementing a SCAL Sample Selection Strategy for a Giant Carbonate Field Offshore Abu Dhabi, U.A.E.

Abstract

Abstract Despite the importance of Special Core Analyses (SCAL) data to the construction of accurate reservoir simulation models, there is a lack of specific industrial guidelines for acquiring core and selecting representative plug samples, particularly for heterogeneous carbonate reservoirs. The aim of this paper is to share the strategy, practices and techniques Zakum Development Company (ZADCO) applied to obtain representative SCAL samples. There are two main aspects to the strategy; (1) coring and (2) plugging. The first stage is determining the parts of the reservoir to target for core acquisition. This requires an understanding of the distribution of static reservoir rock types (SRRT) in the reservoir and their importance to reservoir flow dynamics and fluid storage capacity. The second stage is designing a plugging program to identify reservoir rock types while maintaining the wettability of the samples intended for tests. For the second part, two adjacent sister plugs are acquired, one is a 1 inch diameter plug and the other is 1.5 inch diameter. The 1 inch diameter plug is used for static reservoir rock type (SRRT) identification using porosity, permeability, thin sections and high pressure mercury injection. The 1.5 inch diameter sister plug is preserved to maintain wettability and later used for SCAL measurements. Prior to selecting plug locations, a continuous, 0.5 mm resolution, 3D Computer Tomography scan of the 4 inch diameter whole core is examined. The scan has a high enough resolution that algal and rudist batches are visible. Accordingly, specific rock types are identified visually and targeted. After completion of SCAL measurements, the SCAL plug SRRT is confirmed, utilizing porosity / permeability measurements, thin section description and high pressure mercury injection. The majority of SCAL SRRTs matched the sister plug SRRTs, providing confidence in the technique.