High Salinity Water Flooding in Carbonate and Clastic Rocks: Qualitative and Experimental Analysis

Abstract

Quality of water used for injection is a very essential factor in preventing/minimizing formation damage potential and thus maintaining required injectivity. Also, injected water should be compatible with both rock and formation fluids minimizing risk of permeability impairment or flow assurance problems during the production phase. Assessing water quality is a prime step to prevent scale precipitation, fine migration and any negative impact resulting from water/rock interactions. Extensive experimental studies including HT/HP compatibility tests and coreflooding experiments were conducted to evaluate the effect of high (salinity, sulfates and bicarbonates) water samples on clastic and carbonate core plugs. The impact of rock clay content, fine migration and scale deposition on impairment of rock permeability was investigated. Compatibility and coreflooding tests were conducted on different water mixtures to optimize a water mixture having less effect on formation permeability. Experiments were conducted at temperatures up to 200°F and pressure 3,000 psi. Formation damage mechanisms were investigated using XRD and ESEM methods on precipitated scale due to fluid/fluid and rock/fluid interactions. HT/HP compatibility test results indicated that some of the examined water mixtures precipitated iron compounds when exposed to air. Oxygen scavenger was added to some water mixtures to halt iron precipitation before injection into the carbonate and clastic core plugs. Coreflood experiments showed permeability reduction in some of the core plugs, which was attributed to the precipitation of iron oxide/hydroxide compounds as, indicated from ESEM and XRD analysis. High sulfates and high bicarbonates content of some of the water mixtures precipitated compounds that contain both on the face and deep inside some of the tested plugs leading to reduction in permeability. This paper presents a qualitative and experimental water flooding analysis study conducted to assess interaction of different water/water mixtures on clastic and carbonate core plugs. It also investigates different formation damage mechanisms associated with water injection. It investigates interaction impact of water mixtures with examined core plug permeabilities.