Application of Psudo-pressure ratefunctions in analysis and characterization og gas wells in early stage of field production: A case study of Tanzania's Mnazibay gas field

Abstract

This project is a study aimed at understanding some of the important steps in early characterization of a gas reservoir. The study is based on data collected from MB-3, a second appraisal well drilled on Mnazi Bay Gas field, an Artumas licensed acre age, extending both onshore and offshore Tanzania. The reported data used for both preliminary reservoir characterization and in the reservoir fluid characterization are DST test data, Compositionan alysis from Chromatograph and derivability study from multi rate and the drawdown test data. The report is an extension of a previous work done (last semester) on the same area with more or less same objectives but somewhat different scope. This particular work also includes pressure response study using pseudo-pressure functions.

The PVT data are treated empirically in accordance to some known correlations and principles. The laboratory analysis results are fed into the Eclipse PVTi for computerized fluid modeling on regression Using Peng –Robnson (PR) EOS. Based on fluid composition and the critical parameters, empirical manipulation of properties like Gas Compressibility factor, GasFormation Volume Factor and Viscosity is carried out to model PVT data of the Mnazi Bay Gasfield. On Fluid Modeling, properties of n-C8 are assumed for some missing properties of the heavy fraction, C7+ component.

The analysis took into account the geological assessment based on the MB # 3 original appraisal well log and test data obtained from a drilled, logged and tested MB # 3 well. The well was tested over the C, D, F and G-Sands. RFT data was used to determine pressure distribution profile and fluid contacts which upon Reconciliation with other measured data and geosciences data like the known depositional environment, can then be integrated with reservoir performance and well tests to determine reservoir layering and continuity.

Pressure response analysis and production forecasting of the Mnazi-Bay gas field is discussed and implemented in MS Excel. It is difficult to say conclusively if the use of Pseudo-pressure functions in this particular analysis of MB-3 test data have improved the reservoir model study or not. The noted suddenly fall in WHP might well be greater than the gauge resolution. Theimpact of this impulsive and unprompted drop in pressure readings affected the analysis and interpretation of the pressure data a great deal.