Field Application and Performance Evaluation of Polymer Microsphere Profile Control in Low Permeability Oil Reservoir

Abstract During the development of low permeability oil reservoirs in Changqing oilfield, the nonuniformity of injection profile is a commonly seen problem. Conventional profile control methods face the difficulty caused by hard injection and poor reservoir adaptability. Polymer microspheres (PMs) are considered to have good profile control capabilities due to their properties such as hydration swelling and plugging. Therefore, it is proposed to use PMs profile control method to improve the oil recovery in low permeability reservoirs. There are two key factors for the success of PMs profile control, which are matching relationship and plugging properties. In this paper, the average pore throat diameter of the pilot test area was calculated, and the hydration swelling properties were studied by measuring the diameter of PMs. The plugging properties of PMs were studied by displacement experiment. Based on the experimental research, in 2016, 4 well groups in Changqing oilfield were selected for PMs profile control. Calculation results showed that average pore throat diameter of the study area was 2.28μm. The diameter of 800 nm named PCE been selected for PMs profile control. The hydration swelling experiment results showed that PCE initial average diameter was 784nm. After 13 days of hydration swelling, PCE average diameter was 2798 nm and increased by 2.57 times. The results of PCE displacement experiment showed that resistance factor, blocking rate and retention rate was 3.5, 71.42% and 96.22%, respectively. The performance of the PCE application in oilfield showed that 11 production wells were effective after PCE injection, and the success rate of profile control was 47.8%. The average validity period was 150 days. And a total of 1365.5t of oil had been increased during the validity period. For the injection wells, the average injection pressure and the thickness of water absorbing layers increased by 1.415MPa and 3.28m respectively.