Evaluation of Multiple Geological Models Through Assisted History Matching of Appraisal Well Tests and Early Production Data

MacDonald, David, Marianne Espinassous, Glyn Williams, Mark Mansfield, BP, Sunbury, Middlesex, United Kingdom

Project sanction, the most significant investment decision in most oil and gas develop­ments, is the decision made during the period of greatest uncertainty for the reservoir per­formance prediction. As the industry moves towards deeper water developments, the num­ber of appraisal wells available at sanction will only reduce. Advances in seismic interpreta­tion can in many cases give confidence in the structural and reservoir continuity, but can not be relied on to provide definitive production continuity.

Frequently during the Select and Define stages of a project, significant uncertainty remains in the definition of the geologic model. Frequency, orientation, profile and sinuosi­ty of sand bodies are just a few of the reservoir parameters that need to be characterised before a dynamic model can be built. Understanding and quantifying the uncertainty impact on reserves, rate and NPV should be the principle aim of model studies at this time of field life. It is likely that little can be done to increase the confidence of a single deterministic pre­diction with only appraisal data.

BP’s Top-Down Reservoir Modelling (TDRM) philosophy and toolkit is being successful­ly applied to quantification of the prediction uncertainty in projects from Appraise through to Operate. Specific focus has been made to develop techniques for evaluating multiple geo­logic models by using all available appraisal dynamic data and benchmarks to calibrate the models.

The TDRM philosophy is based on decision-driven analysis and quantification of the impact of reservoir and facility uncertainties on performance prediction using appropriate models. An appropriate model is one which fully characterises the reservoir mechanisms which are significant to the business decision to be made.