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Pressure transient analysis is a veritable technique for reservoir characterisation offering a variety of oil and gas field development information ranging from reservoir permeability, anisotropy, boundaries to wellbore skin, well interference and productivity/injectivity to mention but a few. Well test data acquired at exploration and appraisal stages of oil and gas fields and their interpretation often times need to be re-visited at field development stage when this information are needed to underpin field development plan and reserves assessment. Changing perspective in field understanding as well as advances in well test interpretation may warrant a re-interpretation of pressure transient data from old well tests but at this stage Petroleum Engineers are faced with challenge of unavailability of test data in electronic form to re-visit interpretation with new techniques. Often times data may only exist in paper form. In the quest to grow Africa Oil and Gas production, this paper is sharing a successful investigation of a technique for digitising pressure transient data that exist in paper form into electronic data for the purpose of reinterpreting an old test with recent advances in interpretation technique. The approach is illustrated with results from field testing of a multi-rate test data of a gas well in the Niger Delta acquired and interpreted in the early ‘90s but undergoing field development planning and resource volume evaluation two decades later. Good results were obtained in the field trial, using the techqnique offered in this paper. The re-interpreted reconstructed pressure transient data led to permeability improvement from about 30 to 80 mD using appropriate models in consonance with advances in well test interpretation. This result has been used to update the simulation models for field development planning and reserves booking purposes for the trial field. |
