Production Acceleration in a Key Reservoir by Proactive Well Placement, Utilizing Innovative Logging-While-Drilling LWD Technology in the Vienna Basin, Austria

Abstract

The transgressive sandstones of the Badenian 16.TH reservoir have been on production for over 65 years. As part of a recent field re-development project the oil production has been accelerated with high-angle/horizontal wells. Targeting drainage areas to access attic oil with the accurate placement of these boreholes was deemed business critical. Previous mapping efforts did not capture the undulating structural nature of the top of the first sand layer. Since the "sweet spot" of the reservoir was assumed to have a gross thickness of 1 to 2 meters, the application of proactive geosteering with the latest Logging-While-Drilling (LWD) technology was viewed as essential. This paper describes the placement of two wells, which benefited from active geosteering based on the data transmitted and interpreted in real-time. A multilayer bed boundary detection service was the primary source of information to place the boreholes close to the target formation top and to map the presence of fluid transition zones. Deep azimuthal electromagnetic measurements enabled continuous real-time, 360 degree, mapping of the direction and distance to resistivity changes in the formation. Conventional LWD logs (gamma ray, nuclear, and resistivity measurements) provided formation evaluation and saturation estimation while drilling. The rotary steerable system completed the drill string and ensured directional control. Proactive decision-making used real-time inversions to optimize the landing and improve well placement, since critical data - distance to boundary, geometry of the remote reservoir top and fluid changes in transition zones - were available in real time. In all wells the trajectory was maintained within the zone of interest by taking the proactive, real-time decisions while drilling. The integration of multilayer inversion results with recorded borehole images enabled a comprehensive interpretation and detailed 3D structural modeling in the post-job phase. Sub-seismic faulting and local dip changes were revealed that were not predicted in the pre-drill geological model. Finally, structural information, formation evaluation results, and oil-water transition zone mapping were used to optimize completion design to delay the increase in water production. The production results confirmed the anticipated volumes, proving the advantages of the innovative LWD applications and their capability for optimized placement of such production wells. The use of the directional multilayer detection service aided structural interpretation, definition of the reservoir geometry and the position of the current fluid transition zones. This in turn led to improved accuracy in the description and understanding of the reservoir.