Evaluation Of LTAF Formation Reservoir In The NEB Block Of Jabung West Uplift Zone,indonesia

The LTAF Formation is the main reservoir of the NEB oilfield of the South Sumatra Basin.Its oil and gas production accounted for 75% of the total,but the production formation was found earlier,therefore,after more than 20 years of developing,it has entered into the late phase of development.In order to satisfy the requirements of the development phase and further determine production potential,it is significant of detailed evaluation of LTAF reservoir.In this paper,based on the data of well logging and coring,firstly the LTAF Formation was divided into small layers,then systematic analyzed the sedimentary microfacies,physical properties and heterogeneity.Finally,comprehensive evaluation was conducted.The LTAF Formation was divided into 3 sand members and 15 small layers according to the marker beds,sedimentary cycles and lithologic combinations.Focused on the upper braided fluvial deposition and by establishing sedimentary facies model,the facies markers were summarized.The sedimentary microfacies wee analyzed from single well to profile and then to plane.The result showed that braided channel was dominated by glutenite and log curve was bell-shaped.The point bar was box-shaped or serrated box-shaped and overlaps with each other in section.Upwardly,the fluvial depositional scale gradually increased.The reservoir had high quartz content and the dominant matrix was clay minerals.Pore types were mainly primary intergranular pore and dissolution pore,and the reservoir physical property was commonly good.In the region the porosity and permeability of the small layer decreased from north to south.The heterogeneity of LTAF Formation was evaluated on the basis of inlayer heterogeneity,interlayer heterogeneity and plane heterogeneity.The overall heterogeneity of the reservoir was strong.In the reservoir comprehensive evaluation,selected porosity,permeability and thickness for evaluation parameters,the reservoir was divided into I,II,and III three classes corresponding to the regional actual conditions.Emphasized on demarcating distribution range of each class reservoir of theU1,U2 and U3 small layers,it was proved that the I and II class reservoirs are favorable oil and gas accumulation zones.