Petrophysical And Geostatistical Modelling Of Rex Field, Coastal Swamp, Niger Delta

Abstract

Petrophysical properties such as porosity, water saturation Net to Gross (NTG) and hydrocarbon volumes were estimated and integrated to identify potential hydrocarbon reservoirs, assess reservoir quality and productivity, and estimate hydrocarbon volumes to reduce exploration and development risks. Rex field is located the Niger Delta which is reputed as one of the most prolific petroleum provinces of the world,  found in the Gulf of Guinea on the West Coast of Central Africa. It is located at latitudes 4⁰490 N and longitude 6⁰00 E, The REX Field is located in the coastal swamp at a water depth of twenty-five meters and it is part of a block area a little above 800km² areas in the southeastern Niger Delta. Wells in the Rex Field consist of basic data needed to compute the petrophysical properties that was required for geomodelling except for REX-05 that came with a missing gamma ray log. Composite volume of shale was therefore estimated from other vshale indicators in REX-05. Probabilistic assessment of the reservoirs was done using a probabilistic assessment tool of porosity, permeability net to gross (NTG) and a variogram model was developed. Reservoir petrophysical properties of the REX Field was determined from well log data from six identified reservoirs, the calculated porosity ranged between 0.22-0.32, water saturation was estimated from resistivity logs showing variation between 0.25 and 0.49. Other petrophysical parameters, such as Net to Gross (NTG) for A04, B04, C01 ranges between 0.744-0.99 and net pay between 21- 120. Geostatistical models showed a laterally flattened continuity, with sand-silt facies tested across various reservoirs. The identified oil reservoirs have stock tank oil initially in place (STOIIP) of 190mbo and the gas reservoir with NTG 0.27-0.99 and  net pay range between 21- 130 with a Gas initially in place(GIIP) OF 110bcf. It is therefore recommended that the gas potential of the field be exploited with more concentration on improvement of field development methods