The Vietnam Petroleum Institute (VPI) is implementing a multi-task national level project entitled “Research, evaluate, select and develop a pilot programme for industrial application of solutions to improve oil recovery coefficient for clastic oil bearing reservoirs of oil fields in the Cuu Long basin, on the continental shelf of Vietnam”. Specifically, detailed evaluation studies have been carried out from geological characteristics, reservoir engineering, production to EOR mechanism to develop technical criteria for the process of manufacturing and evaluating the efficiency of the chemical system to optimise the laboratory scale, propose the production and injection scenarios to optimize the development plan as well as evaluate the efficiency of increasing oil recovery coefficient on the reservoir simulation model; conduct production at pilot scale and implement industrial application testing on the field scale for clastic oil bearing reservoir, Cuu Long basin. The article presents the results of research, evaluation, selection and successful manufacture of a VPI SP chemical system based on the combined mechanism of anionic - non-ionic surfactants and polymers to ensure satisfying the harsh technical requirements of oil fields in Vietnam such as resistance to high temperature, high pressure, high mineralisation, very low surface tension, optimal micro-emulsion, low adsorption onto reservoir rocks, reducing residual oil saturation in the reservoir. Results of the evaluation of increased efficiency of oil recovery on actual samples of Miocene reservoir showed an increase of over 21%. The VPI SP chemical system has been included in the plan of industrial-scale testing by Vietsovpetro in Bach Ho and other producing fields in the clastic sections of the Cuu Long basin.
The objective of this study is to identify the sources of the formation water in the Southwest Su Tu Den (STD SW) basement reservoir. To achieve the objective, isotopic techniques along with geochemical analysis for chloride, bromide, strontium dissolved in the water were applied. The isotopic techniques used in this study were the determination of water stable isotopes signatures (δ2H and δ18O) and of the 87Sr/86Sr ratio of strontium in rock cutting sample and that dissolved in the formation water. The obtained results showed that the stable isotopes compositions of water in the Lower Miocene was -3‰ and -23‰ for δ18O and δ2H, respectively indicating the primeval nature of seawater in the reservoir. Meanwhile, the isotopic composition of water in the basement was clustered in a range of alternated freshwater with δ18O and δ2H being –(3-4)‰ and -(54-60)‰, respectively). The strontium isotopes ratio for water in the Lower Miocene reservoir was lower compared to that for water in the basement confirming the different natures of the water in the two reservoirs. The obtained results are assured for the techniques applicability, and it is recommended that studies on identification of the flow-path of the formation water in the STD SW basement reservoir should be continued.
Pore pressure can be obtained from seismic interval velocity by the velocity to pore pressure transform technique. In this paper, the authors present the Eaton experimental method to calculate pore pressure for some wellbores in the Cuu Long and Song Hong basins, where complex processes of subsidence, burial, geological transformation, and geothermal activity took place, causing abnormal pressure zones.The obtained results show that the pore pressures calculated from the seismic interval velocity data are closely correlated with the values measured by well logging methods and the density of the drilling fluids. Therefore, using seismic interval velocities to calculate pore pressure values, identify and predict abnormal zones by the Eaton method can be effectively applied in frontier areas to improve safety, reduce risks while drilling.
Enhanced oil recovery (EOR) implementation at field scale is complex. Therefore, pilot applications are usually conducted before field execution. This paper introduces a pilot project successfully applied for the Lower Miocene, Bach Ho field. Topics covered include: (i) pilot area selection, (ii) chemical preparation, (iii) specification and pilot design for execution, (iv) implementation, (v) pilot observation and interpretation, (vi) efficiency evaluation. The implementation of pilot projects is achieved on 23 January 2022. The evaluation shows that 2,700.2 tons of oil gained thanks to the application of the surfactant-polymer complex mixture (VPI SP).
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