First SPE Workshop-Webinar Held on Waterflooding
The Technical Aspects of Waterflooding workshop held 23 October in Long Beach, California, was the first SPE event to involve both live participants and members participating around the world through a real-time video feed.
The workshop drew more than 70 participants from various companies and organizations, including Occidental, Signal Hill Petroleum, Berry Petroleum, Santa Maria Energy, Termo, Spec Services, the California State Lands Commission, SPE board members, and students from the University of Southern California and California State University of Long Beach. The workshop was held by the SPE Los Angeles Section and the one-day live webinar by SPE. Following are highlights from the workshop.
When Water and Oil Mix
Water and oil sometimes mix due to formation of certain structures known as emulsions, small droplets of water in oil or small droplets of oil in water that add surfactants. Some complex molecules in oil may cause formation of emulsions without adding surfactants. Emulsions in production facilities are well known. Functionalized molecules are added in small quantities to separate oil and water. The formation of water-in-oil emulsion in the reservoir is very undesirable because of the high increase in viscosity and low recovery. Oil-in-water emulsion formation is desirable for improved oil recovery. The talk centered on mixing of oil and water when water-in-oil emulsion is formed. Extensive results from laboratory core flooding were presented to demonstrate that when water-in-oil emulsions are formed from the contact of water and oil, the flow has many complexities. These include pressure decrease in the core at high injection rate and substantial pressure increase when water enters the core. To alleviate the problem and recover oil from the conditions in which water and oil mix, the best option is addition of small amounts of functionalized molecules that invert the water-in-oil emulsion to oil-in-water emulsion.
Waterflood Management and Surveillance
This presentation illustrated how practical application of surveillance and monitoring principles are key to understanding reservoir performance and identifying opportunities that can improve oil production and ultimate oil recovery. Implementation of various principles recommended by industry experts were presented using examples from fields currently in production. Examples of how to process valuable information and analyze data from different perspectives were presented in a methodical way on the following bases: field, block or zone, pattern, and wells. A novel diagnostic plot, called the ABC Plot, was presented to assess well performance and identify problem wells for the field. Results from the application of these reservoir management and surveillance practices in a pilot area were shared, indicating that the nominal decline rate improved from 33% to 18% per year without any infill drilling. The change in the decline rate was primarily attributed to effective waterflood management with a methodical approach, employing an integrated multifunctional team. Although the suggested techniques can be applied to any oil field undergoing a waterflood, they are of great value to mature waterfloods that involve significant production history. In these cases, prioritization is a key aspect to maintain focus on the opportunities that can add most value during the final period of the depletion cycle.
Waterflooding Process and Design
Waterflooding as a process is the most widely used post-primary recovery method in the United States and contributes substantially to current production and reserves. Waterflooding consists of injecting water into a set of wells while producing from the surrounding wells. It maintains reservoir pressure and displaces oil from the injectors to the producers. Waterflood recovery efficiency=displacement efficiency within the volume swept by the water×areal sweep efficiency×vertical sweep efficiency. Displacement efficiency is affected by rock and fluid properties, and throughput (pore volume of water injected). Areal and vertical sweep efficiencies are affected by flooding pattern types, mobility ratio, reservoir heterogeneity, and throughput. Waterflood design considerations are reservoir characterization, potential flooding plans, estimation of injection and production rates, facilities design, capital investments, operating costs, and economic evaluation. Satter emphasized the following: Build integrated geoscience and engineering model using available data, simulate full-field primary performance, and forecast performance under peripheral and pattern waterflood drive. Choose peripheral and pattern development cases. Make economic analysis of the chosen cases using waterflood oil recoveries obtained, and capital investments to determine which case would be more profitable.
Waterflood on a Chip
Baldev S. Gill
Microfluidics are used to displace one phase with another in a water-wet prefabricated microchip and the displacement can be seen under a microscope. In Gill’s example, synthetic oil was displaced with deionized water using equipment from a laboratory at the University of Alberta, Canada. In essence, this talk discussed the concept of “reservoir on chip” (ROC). The process includes several steps, from taking a core from a reservoir rock and creating a series of micro-structure images in FIB-SEM and then constructing a 3D model of the reservoir pore space. From this, a pore network is extracted and a realistic 2D pore network is developed from the cross-section of the 3D network. This network is finally etched on silicon and the ROC is developed. A video is developed that highlights when the chip is originally saturated with oil and then a blue dye is introduced with the water velocity to show the displacement efficiency as the number of pore volumes increase. Of particular interest is the entrapment of oil globules around the pore throat network, which highlight the capillary pressure influence on the pore throat size and the bypassing of oil once the water breaks through.