Selective and Reversible Water Shut-Off Agent Based on Emulsion System with Nanoparticles Suitable for Carbonate Reservoirs at High Temperature and High Salinity Condition

Abstract

Abstract This paper presents the evaluation results of water shut-off (WSO) agent based on emulsion type chemical material with nanoparticles. The WSO agent called Emulsion System with Nanoparticles (ESN), it has several unique advantages to existing polymer and gel materials; high thermal stability, low sensitivity to mineralization, thixotropic characteristic, selectivity of blocking effects for oil and water, and reversibility of blocking effect. In WSO application, these properties of ESN could be a good match for the tasks of improved oil recovery. Also, the surface modified silica (SiO2) nanoparticles have an important role to drastically enhance stability of the emulsion system. The ESN can be prepared easily by mixing emulsifier and silica nanoparticles with the on-site oilfield materials such as crude oil and brine. The refined diesel oil can be used for ESN preparation instead of crude oil, so it will be an option depending on the situation of target oil field infrastructure and operator's policy. To evaluate the performance of ESN as WSO agent for UAE's carbonate reservoirs, core flooding tests using low permeability carbonate cores with different water saturation were performed at high temperature condition. The ESN, which is confirmed to be stable at 120 °C and 240,000 ppm TDS, achieved 85 % permeablity reductions for intermeaiete and high Swi cases of the core flood tests. The relative permeability analysis confirmed unblocking by oil inflow for intermediate and low Swi cases. Through comparative analysis and discussing these test results, the laboratory study investigated technological potentials of ESN to block water zones and control water cut of oil wells. This paper introduces the detailed evaluation results of ESN and possibility to successfully apply it for UAE's oil fields in the future.