Integrated Approach to Address Reservoir Uncertainties in One of the Largest Recent Gas Discoveries Onshore Egypt

摘要

The BTE field is one of the largest recent gas discoveries in the Egyptian Western Desert. The main subsurface uncertainties impacting the Initial Gas in Place (GIIP) are Gas Water Contact (GWC), structure, fault positions and sand development. Given the large subsurface uncertainties, it is planned to further appraise the field with one or two appraisal wells and reshooting seismic. Other key uncertainties are sand quality, intra-field faults and aquifer strength. These uncertainties will impact the wells deliverability, Estimated Ultimate Recovery per well (EUR/well) and the Ultimate Recovery Factor (URF). The EUR/well and the URF are a function of the number of wells drilled. An integrated probabilistic modelling (experimental design model) approach was developed to consider all main reservoir uncertainties together and determine the true P90, P50 and P10 EUR subsurface realizations. Three different software packages were used and linked together; Material Balance Equation1-3 (MBE) software, statistical 4 package software, and Spreadsheet software. The three packages are talking to each other through Visual Basic for Application5 (VBA) programming language. This probabilistic model enables the user to run sensitivity studies by changing one parameter at a time and check its effect of EUR. The model also lends itself for uncertainty studies (experimental design) by examining all the possible combinations scenarios between the different uncertain parameters; such as GIIP, tanks transmissibility, wells flow coefficient 6 (C), wells flow exponent (n), relative permeability parameters, aquifer properties7, etc.