Pressure volume temperature evaluation of Sapele Field, Niger Delta, Southern Nigeria

Abstract

Sapele field is a large, brown field with complex subsurface structure that has led to heavy compartmentalization of its reservoirs which has also resulted to low reservoir pressure in some parts of the field leading to low production output. Reservoirs were delineated at various depth, some at near surface area (Benin formation) while others at greater depth (Agbada formation), hence the field was further subdivided into two (Sapele Shallow and Sapele Deep) due to its structural complexity. Pressure Volume Temperature (PVT) laboratory analysis on different wells was available for this study and the viscosity of the reservoir fluid was measured using an Electromagnetic Viscometer (EMV) at reservoir temperatures of 129 ⁰F and 207 ⁰F. These data were used in determining hydrocarbon chemical composition, its viscosity, specific gravity, density, and American Petroleum Institute (API) unit. Sapele Shallow reservoir is made up of heavy oil as its hydrocarbon content as a result of biodegradation process in which micro-organisms degrade the light hydrocarbons due to the shallow nature of the reservoir in the field, making it rich in heavy molecular weight hydrocarbon compounds. While Sapele Deep is made up of heavily compartmentalized reservoirs with gas and light oil as its hydrocarbon content. Hence the field requires different exploitation and production approach to fully annex its reservoir hydrocarbon content.