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Between July 2018 and January 2019, Shell acquired two vertical seismic profiling (VSP) surveys in two deepwater wells in the Gulf of Mexico by using a seismic while drilling (SWD) tool. Each survey included a rig source zero-offset VSP and a boat source offset VSP. The main objective of the surveys is to delineate the salt-sediment boundary at the salt base and flank. We design and execute the complex VSP surveys with emphasis on optimization, efficiency, and integration. We develop a comprehensive analysis and processing method to integrate P-wave sediment and salt proximities with converted PS salt proximity. We use SWD-VSP surveys to demonstrate how we define the salt boundary with the integrated results. Our results show that we can delineate the salt boundary with better accuracy and with a high degree of confidence. These successful VSP surveys provide significant business and technical value.

Monobore completions have been installed in wells as far back as the 1980's. Early examples were reported in several SPE papers by companies such as Santos, Total and Unocal (now Chevron). The main drive being reduced drilling and completion costs. Perforating monobore completions is also not new and there are several methods to deploy guns into these types of well completions under various conditions (underbalance, overbalance or dynamic underbalance). Reservoir performance can be optimized through perforation modeling where analysis has shown that a tailored Dynamic Underbalance (DUB) approach can deliver productivity gains from 5% (shallow mud filtrate damage) to 40% (deeper mud filtrate damage) higher than traditional perforation techniques. This is a data driven optimization based on field data such as zonal permeability, pressure, temperature, fluid shrinkage factor, fluid viscosity, GOR, wellbore trajectory and completion design. To achieve maximum gain, multiple perforating runs on wireline are required; however this approach is often discounted (with well life production sacrificed) in order to achieve rig efficiency targets within the constrained economics of monobore completions, and to limit HSE exposure. This paper discusses a pragmatic approach to perforation optimization focusing on the specific alignment of economic, technical and safety related aspects within oilfield operations. The context of this approach applies to the techniques used to avoid rig critical path altogether, thus removing rig cost from the equation and refining the approach through a data driven workflow utilizing acquired DUB pressure data. This approach describes the combination of the key components in detail, including latest shaped charge design and perforating technology, workflow optimization, operational risk and execution approach. Results within this case have led to a standardized workflow within monobore completion delivering more than 24 days in operational savings over a 12 month period, and post perforation nodal analysis showing gains of up to 40% within a mature asset.

This paper outlines our results and experiences in hydrocarbon typing Pliocene/Pleistocene turbidite sand reservoirs in two Shell Offshore Inc. Gulf of Mexico fields. While differentiation of hydrocarbon type was important in identifying completion targets for Produce While Drilling (PWD) operations, hydrocarbon typing was extremely difficult. This hydrocarbon typing problem was a result of (1) compositional make-up of both oil and gas, (2) high reservoir pressures encountered (up to 10,000 psi), (3) geological complexity (structural and stratigraphic), (4) the use of oil based mud to drill many wells, and (5) complex mineralogical makeup of the sands.Because openhole data and routine pulsed neutron capture (PNC) data were often inconclusive, secondary curves presented on PNC logs were extensively examined. The PNC ratio of inelastic short to long spaced data (RIN) was found to be an extremely diagnostic gas indicator, and has been used to further refine and calibrate petrophysical evaluations. These refined evaluations were then incorporated into redesigning a new completion strategy for each well examined. ScheibalWeiland Worrell Bayer