Integrated study of the reserve estimation of Narshingdi gas field

Abstract

Demand of natural gas is always higher than the supply in Bangladesh. Correct estimation of reserve is important for the development of the gas fields, design of production facilities and preparation of the gas contracts. Narshingdi is one of the gas fields of Bangladesh Gas Field Company Limited (BGFCL). This field was discovered by Petrobangla in 1990. The objective of this study was to estimate the Gas Initially In Place (GIIP), remaining reserve, reservoir boundary, and various petrophysical data of Narshingdi gas field. There are two gas sands, Upper Gas Sand (UGS) and Lower Gas Sand (LGS) in this field. Gas production started in 1996 and presently the two producing wells (NAR-1 and NAR-2) are producing gas from LGS at a rate of 17 and 11 MMSCFD respectively. Seventeen years of production data (1996 to 2013) have been analyzed to perform material balance and advanced decline curve analysis. Monte Carlo simulation approach was also performed to estimate proved, probable and possible reserve. Reservoir simulation using ECLIPSE 100 black oil simulator was performed for the purpose of history matching and production forecast. Different forecast scenarios were designed to investigate the effect of additional vertical well and gas compression on recovery. The regular pressure survey of the field was not conducted and therefore Flowing Gas Material Balance an alternative to conventional material balance was performed. In the absence of pressure transient test (e.g., buildup, drawdown) data, advanced decline curve analysis was performed to calculate the reservoir potentiality (permeability, skin), reservoir area, GIIP and the ultimate recovery of the field. This study shows that the reservoir is depletion type and the pressure decline is significant. Adding more well in the lower gas sand will not be beneficial.