Gel Treatments Pilot Test in Conventional Heavy Oil Reservoirs of China Offshore Oil Field

Abstract

More than 80% oil resources were heavy oil in Bohai Bay of China. Generally, we used water flooding in the reservoirs with the viscosity less than 400cp. But there were many challenges during water injection in conventional heavy oil reservoirs because high oil-water viscosity ratio lead quick breakthrough of injecting water. And with the oil-water viscosity ratio increasing, the breakthrough of injecting water became more serious. In order to solve these problems, the gel treatments on the injection wells pilot test were conducted in x oilfield during the year 2009 to 2011. Before pilot test, laboratory study under field conditions was conducted to determine the chemical parameters of the gel. We also did numerical simulation study with CMG. A range of variation of critical parameters was evaluated in the simulation for understanding the gelation process undergroud. The model was used to predict the reservoir response under different chemical parameters. Results from simulation showed that water cut reduction ranged from 15.9 to 36.6% which matched the trends observed in wells. On the other hand, dynamic method was also used to evaluate the gel pilot test. The Hall curve analysis was used to evaluate the effectiveness of the injection well and to calculate the resistance factor (RF) & residual resistance factor (RRF) (RF from 1.82 to 6.88, and RRF from 1.29 to 7.97). The decline curve analysis was used to obtain net incremental oil by gel injection treatment. Results from two well patterns conducted gel pilot test in 2009 indicated that water cut reduction ranged from 3.2 to 36.8% and average oil production increases 15.7m3/d. Based on results, another two wells in 2010 and two wells in 2011 were conducted, and we received good effectiveness by gel treatments. The pilot test & evaluation technology provide the foundation for promoting application of techniques to stabilize oil rate and control water production in conventional heavy oil reservoirs of China offshore oilfield

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