Effect of Temperature on the Rheological Properties of Eastern Ogun Oil sand Slurries Formed with Water or Diesel

Abstract

Slurries are formed during the flooding of oil sand in the subsurface and the formation of these slurries between injected fluid and heavier oil in the oil sand will create both in situ separation of oil from the grains of the oil sand and an increase in the mobility of the oil for production purpose.  The increasing mobility is due to density and viscosity reduction as a result of increased temperature. This research studied the rheological properties of the slurries obtainable when tropical oil sand deposits are either flooded with hot water for enhanced production or when diesel is injected into the oil sand formation in preparation for an in-situ combustion. The main focus is the analysis of the rheological properties of the slurries formed as indication of mobility of the oilsand slurries during future development of the long-abandoned Nigerian oil sand deposits. Obtaining an optimum slurry mixture will result in optimize flow rate during production. The optimum mixing ratio of the oil sand and the injected fluids were obtained through series of mixing ratios until the resultant slurry formed was homogenous mixture, for both the diesel and the hot water. This gives approximate volume of the hot water or the diesel to be injected per unit volume of the oil sand with special consideration to the top layer temperature of the oil sand reservoir. Moreover, the knowledge of the rheological properties obtained in the research will help in the design of the surface equipment (Annudeep 2012; Brookfield 2016) required for the heavy oil production. The unprocessed oil sand used in this research was mechanically mined, at Imeri-Ogun, Nigeria, in order to simulate probable in-situ slurry obtainable for hot water flooding of the oil sand for heavy oil production or for in situ combustions of the oil sand with diesel.  It was concluded that the reduction in the gel strength of oil sand-water slurry with increasing temperature will result in less sand grain production during the flooding of the oil sand with hot water. It was discovered that at a slurry temperature beyond 60^oC, slurries formed will be too viscous for effective flow because of higher solubility between the oilsand and the solvents.

Keyword: oil sand; rheological property; slurry; drilling mud; viscosity; in situ flooding.