Evaluation of Asphalt Particle for Impeding Channeling and Enhance Oil Recovery in Naturally Fractured Reservoir

Abstract

Channeling is one of the major problem for water flooding reservoir, causing excessive water production and low recovery. Chemical methods are commonly used for plugging thief zone and modifying profile in many oilfields. This paper describes a profile control process using asphalt particle in a naturally fractured reservoir located in Fuyu oilfield, China. Average permeability of the reservoir is 180mD and average porosity is 25%. Most of the wells in this reservoir are facing severe channeling problems, with average water cut of 96% before treatment. It was identified that mainly two channeling patterns were existed, including large pore channeling and fracture channeling. Detailed adaptability study was carried out by a series of cores flooding. Result shows asphalt particle polymer gel system has significant advantage compared with pure polymer gel for plugging hydraulic fracture channeling, with a permeability reduction more than 90%. Under the formation temperature, asphalt particles bonded together and stuck in the fracture to form a strong blocking ability. Totally 131.4t asphalt particle (0.02~0.06mm) with more than 50000m3 polymer gels (3000mg/L) were successfully injected into 38 wells. The proportion of effective production wells in this reservoir is 81.3%. The treatment resulted in a field oil increase of 29.9 t/d and water cut decrease of 4.6% in one year after treatment. The asphalt particle was proved to be a suitable profile control agent for such reservoirs facing problem of hydraulic fracture channeling. Besides, in order to find out the reason of differences in the degree of effectiveness for different well group, numerical simulations were carried out to study the influence of geological parameters and injection parameters to the profile control performance by asphalt. It was found that the fracture density and width had an important role to the effectiveness of profile control. Results of the sensitivity study will provide guidance for the design of channeling plugging process by asphalt particle.