Real-Time High-Resolution LWD Images Used to Navigate a Carbonate Reservoir

Abstract

Abstract The Permian basin of West Texas is one of the most mature and prolific oil provinces in the US, and continuously evolves in its production potential via the drilling of horizontal wells. A vital element to accelerate ROI is to accurately place the wellbore in the target formation. Determining and identifying the zone of interest within the carbonate interval and then navigating within it with conventional LWD technology has become a major challenge. To overcome these challenges, real-time high-resolution LWD images were proposed. Azimuthal gamma ray and multiple propagation resistivity measurements were used to determine bed dip, correlate position within the reservoir and indicate formation porosity variations. Advanced LWD imaging tools provide visual confirmation of steering up and down within the reservoir and identify structural information, porosity changes, rock type, faults and the location, density and type of fractures. This paper provides examples of reservoir navigation techniques along with the increased precision provided by imaging tools. Previously undetected faults, brecciated intervals, and fractures are identified. This enables a more precise completion design that reduces risk and increases production. Using this method, the percentage of the lateral interval in zone was increased to 100% from 77% in an offset well. Images of lateral variations in the formation will be presented. This information was used to optimize the completion design and is invaluable in the planning of future wells. LWD images are used to more efficiently drain the reservoir by providing the necessary information to stay in the target zone during longer intervals and assist completion optimization. LWD images can also be used to help explain production variances commonly observed between wells targeting the same interval. Geological Background The Permian Basin is a sedimentary basin largely contained in the western part of Texas and the southeastern part of New Mexico (Fig. 1). It is so named because it has one of the world's thickest deposits of rocks from the Permian geologic period. The Permian Basin was deposited from Ordovician through Mississippian time, and is deepest just west of Midland. It was uplifted at the end of the Devonian and early Mississippian periods. Tectonic activity at the end of the Mississippian period created the Midland Basin to the east, the Delaware Basin to the west and the Val Verde Basin to the south. During the Pennsylvanian and Wolfcamp periods, the basin was favorable to reef growth and the building of shelf margins on the edges of the Delaware and Midland basins. The last major geological development was the Permian Reef Complex, which developed on the border of the Delaware Basin. (J. Michael Party 2012)