A New Approach to Quantify Gross Rock Volume Uncertainty - Application to a Carbonate Reservoir, Offshore Abu Dhabi

by K.I. Hosani¹, T. Matarid¹, S. Walia², and S. Das²

Abstract

Gross Rock Volume (GRV) uncertainty is extremely important in the early phases of field appraisal and development. The traditional approach to quantify the GRV uncertainty is by using a combination of seismic interpretation, velocity modeling and fluid contacts. In this paper, a new approach will be introduced allowing users to define both lateral and vertical uncertainties at every pick during the seismic interpretation workflow alongside velocity models and fluid contacts. This approach will enable users to integrate seismic uncertainty with the structure modeling uncertainties in a single workflow. The new approach has been applied to a carbonate reservoir, offshore Abu Dhabi, at an early stage ahead of field development. The field was covered with 3D seismic data in 2007 and limited number of wells were penetrated the targeted reservoirs. The objective of the paper is to estimate P10, P50 and P90 of the GRV values with respect to the limited available data. The paper will clarify the steps of defining, utilizing seismic interpretation, vertical and lateral uncertainties for every pick of horizons and faults based on seismic signal quality. As a result, a standard deviation map for each horizon is produced along with base horizons and faults that will define the variation of horizons between the wells. Similarly, based on geological knowledge of the reservoir and seismic signal quality, various faults parameters such as lateral position, dip, strike and throw can be incorporated within a defined range to run multiple realizations. This generates not only the P10, P50 and P90 for GRV values, but also evaluates the impact of horizons, velocity models and fluid contacts on the GRV calculation. The results for the operator offshore Abu Dhabi as well as other Middle Eastern operators will be improved GRV uncertainty and valuable input into field appraisal and development plans.

AAPG Search and Discovery Article #90188 ©GEO-2014, 11th Middle East Geosciences Conference and Exhibition, 10-12 March 2014, Manama, Bahrain