Journal of Emerging Trends in Engineering and Applied Sciences: Research Areas

Article Title: Rock Physics Diagnostic for Enhancing Characterization of Reservoir Sands within Offshore Field, Niger Delta
by Abe, Sunday James, Akinyemi, Oluwaseun Daniel and Olatunbosun, Moses Oluwatope

Abstract:
Petrophysical and rock physics analysis were utilized to provide more insight into reservoir sands quality in a field within Niger Delta Basin. The qualitative interpretation previously carried out on this field has resulted into lesser expected outcome. Hence, the need to understand the reservoir attributes quantitatively in this field become necessary. Suite of wireline logs from four well were used. Major lithologies were identified using gamma ray log. Hydrocarbon and non-hydrocarbon bearing sands were delineated using the combination of gamma ray and resistivity log responses. Reservoir rock properties of the intervals of interest was computed using well-established relationships. Rock physics diagnostic of the sediment helps to quantitativelyclassifylithologies and fluids. It also provide insight the nature of reservoir sediments using Han Model. The stratigraphy of the delineated lithologies is intercalation of sand and shale layers. The shale layers was observed to increase in thickness with depth and the sands decrease in thickness. Two reservoirs labelled as RES-1000 and RES-2000 were delineated. Reservoir RES-1000 has average volume of shale of 12 %, effective porosity 25 % and permeability 1451 mD. Reservoir RES-2000 has average volume of shale of 16 %, effective porosity 22 % and permeability 907mD.The statistical reservoir parameters ranking indicated that the two reservoirs have medium to high connectivity and hydrocarbon potential. Rock physicscrossplotsof acoustic impedance against shear impedance, velocity ratio against acoustic impedance and Mhu-rho against Lambda-rho helped to classify the study field into three zones; hydrocarbon sands, brine and shale. The discrimination of reservoir fluids was clearly observed by large separation between the gas sand and background trend on the crossplots. Clay volume analysisutilizing Han model performed on the sediment revealed that the compaction of sediments in study field has both depth related diagenetic and depositional environment influences. The results obtained from this research provides insights into integrated reservoir attribute assessment that aided in unraveling of complex geological settings for exploitation of hydrocarbon in the study field and can hence be adopted in future studies.

Keywords: Rock Physics, Characterization, Clay Volume, Reservoir Quality, Ranking Assessment, Crossplots

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