ANALYSIS OF THE DRIVE MECHANISMS OF THE SONGO SONGO GAS FIELD

Abstract

This report focuses on establishing the drive mechanisms of the Songo Songo gas field inTanzania. The thesis is based on determining the presence or absence of aquifer, determining type of aquifer, size of aquifer, aquifer properties and aquifer strength as well as suggesting the best way of producing the reservoir under the identified drive mechanism. In this work two main methodologies were involved. First, perform material balance analysis using p/Z vs cumulative gas production (Gp) plot to study the presence of aquifer characteristics. Second, perform simulation of the Songo Songo reservoir simulation model using CMG-IMEX simulator under Carter-tracy and Fetkovick methods for aquifer cases and history match using aquifer as the history matching parameter to stufy the effect of aquifer to the reservoir performance.The aquifer cases involved simulating the reservoir with no aquifer, with boundary aquifer, with bottom aquifer and then with both aquifers. After that history matching the results was done to determine which case matches better to the actual data which will be used to conclude the analysis.In order to accomplish this report, the following chapters are presented. Chapter 2 describes the Songo Songo gas field which is the case study of this thesis. Chapter 3 gives the theory on aquifer analysis describing the main concepts in understanding aquifer analysis. Chapter 4 gives the summary of the literature surveyed concerning the four concepts described in Chapter 3.Chapter 5 describes the CMG-IMEX simulator and the Songo Songo reservoir simulation model. Chapter 6 elaborates the material balance and simulation work. Results and discussion are found in Chapter 7 where all the findings are analyzed and discussed. Chapter 8 gives the conclusion and recommendations of this thesis. Chapter 9 defines the abbreviations used in this report. References used in this work are outlined in Chapter 10 and the lastl is Chapter 11 which contains appendices that show other tables, data and conversion factors used in this work.From this thesis the Songo Songo gas field is found to be driven by two drives, volumetric drive which provides much of the pressure support in earlier time (before 2012) and aquifer drive which until 2013 was giving little pressure support to the gas production. In the future the study indicates that there may be more pressure support from the aquifer to the gas production. The aquifer present is bottom type and is a strong aquifer. The aquifer present is estimated to be largeaquifer with permeability of 50mD and porosity of 20%.