Waterflood Potential of Diatomite: New Laboratory Methods

Abstract

Diatomite reservoirs in the San JoaquinValley contain vast reserves in high porosity, thick pay zones. Waterflooding ~ould substantially increase recovery if ~mplemented successfully. Unfortunately the presence of fractures in a low perme~ bility matrix makes waterflooding difficult to evaluate by conventional methods. Presented here are unique laboratory methods and results of laboratory tests designed to provide operators with data to better evaluate the secondary recovery potential of diatomite.Subsidence-oriented compressibility tests revealed extreme sensitivity to standard core cleaning and drying procedures. All subsequent tests, including brine sensitivity, relative permeability, and spontaneous imbibition were performed following miscible solvent cleaning with no drying step. Spontaneous water imbibition was ~nvestig~ted in detail, showing prom~se for oil movement from the tight matrix into adjacent fractures during a waterflood.

Heavy and Thermal Oil Recovery Production Mechanisms

“…Thus, injectivity is low (unless samples are severely fractured), the rock matrix is relatively fragile, and generalization of results across rock type from chalk or sandstone to diatomite is not currently possible. To our knowledge, the first X-ray CT images of diatomite undergoing water injection are given by Wendel et al (1988). Subsequently, spontaneous co-current and counter-current imbibition characteristics were imaged in outcrop with X-ray CT for a variety of mobility ratios, at room temperature.…”