Reservoir characterization in the Captain Field: integration of horizontal and vertical well data

Abstract

The Captain Field lies in UKCS Block 13/22. It is a large viscous oil field with an excellent quality Lower Cretaceous sandstone reservoir. Development of this high viscosity crude (88 cp at the in situ temperature, 87°F) in the offshore environment was possible only after the development of reliable horizontal drilling technology, combined with high volume down-hole electric pumps, and the ability to run long pre-packed sand control screens. As the first development of this type within Texaco, the development decision was helped by the extremely favourable reservoir conditions present in the Captain Field.The Captain reservoir is encountered directly beneath the chalk and consists of Late Aptian aged turbidite sandstones, with high porosity (av. 31 %) and permeability (av. 7 D). The sandstones were deposited on the feather edge of a large turbidite fan system derived from the East Shetland Platform to the north and which thins onto the Captain Ridge. The reservoir sequence consists of two principal sand bodies, the Upper and Lower Captain Sandstones with contrasting reservoir geometry. The Upper Captain Sandstone is developed in a continuous sheet that systematically thins and pinches out to the southeast whereas the Lower Captain Sandstone is concentrated in a sand fairway, interpreted to be a back-filled submarine canyon cutting across the Captain ridge. Core description show the sandstones to be predominantly massive suspension fall out sediments (S3 deposits, Lowe 1982) with rare intra-reservoir claystones.In this paper the reservoir geometry and sedimentology of the Captain Sandstone Member is described with particular attention being drawn to how horizontal drilling has tested and enhanced the geological model. Key reservoir parameters (e.g. connectivity, claystone distribution, grain size distribution, porosity, horizontal and vertical permeability) are discussed and their contribution to the success of the project evaluated.

Multiphase Flow Characteristics of Heterogeneous Rocks From CO2 Storage Reservoirs in the United Kingdom

“…The Captain sandstone core had a permeability of 1.1 D and porosity of 0.27, similar to samples from the Goldeneye field (Hangx et al, ; McDermott et al, ). Much of the Captain sandstone formation is poorly consolidated and in the Captain field permeabilities over 7 D are not uncommon (Lach, ; Rose, ). However, a more consolidated and hence lower permeability core sample was obtained due to the difficulties of drilling core from poorly consolidated sandstone.…”

Multiphase flow characteristics of heterogeneous rocks from CO2 storage reservoirs in the United Kingdom

“…The Captain sandstone core had a permeability of 1.1 D and porosity of 0.27, similar to samples from the Goldeneye field (Hangx et al, 2013;McDermott et al, 2016). Much of the Captain sandstone formation is poorly consolidated and in the Captain field permeabilities over 7 D are not uncommon (Lach, 1997;Rose, 1999). However, a more consolidated and hence lower permeability core sample was obtained due to the difficulties of drilling core from poorly consolidated sandstone.…”

Repeated cycles of submarine channel incision, infill and transition to sheet sandstone development in the Alpine Foreland Basin, SE France

“…Several economic hydrocarbon accumulations are thought to be hosted within incised, deep‐marine turbidite channel systems (e.g. Rose, 1999). Within such fields, a key development issue may be the degree of sandstone connectivity, both intrachannel and extrachannel, including channel–channel and channel–substrate connectivity (Larue & Friedmann, 2000).…”