Techbits: Comprehensive Look at Chemical Flooding Includes Mobility, Surface Gathering
Authors: JPT staff _ 
Published: February 2015

A tour of the pilot and large-scale chemical floods under way in the Daqing field drew the attention of 135 people from 39 organizations and 14 nations at the Applied Technology Workshop (ATW) on Chemical Flooding held in Daqing, China. The keynote address by ATW Cochairperson Wang Demin of Daqing Oilfield Co. described the development of the Daqing field and emphasized enhanced oil recovery (EOR) efforts. There were seven technical sessions. The session was cochaired by Randy Seright of New Mexico Tech.

Objectives of the ATW were:To review why chemical-flooding projects declined in the mid-1980s.To review state-of-the-art processes of chemical flooding.To gain firsthand knowledge of recent chemical-flooding applications in China in recent years.To identify technical and economic challenges that must be overcome before chemical flooding will become commonly applied.

Session 1 discussed chemical-flooding mechanisms. For polymer flooding, recent research suggests that viscoelasticity may contribute to displacement efficiency. For alkaline-surfactant-polymer (ASP) flooding, optimal salinity and low interfacial tension (IFT) can correlate with soap/surfactant ratio. A gradient of soap/surfactant ratio can assure passage of displacement profile through low IFT. Low tensions may be possible in the lower phase microemulsion region, resulting in a wide low-IFT region. ASP flooding improves recovery by displacement efficiency in high-permeability layers and by sweep efficiency in lower-permeability layers. Enhanced recovery in oil-wet, fractured carbonate-matrix blocks occurs by gravity drainage through alkali and surfactant-altering wettability and moderately lowered IFT. Ultralow IFT is not necessary.

New chemicals were presented in Session 2. Several new polymers were discussed, including hydrophobic associative polymers, a salt-resistant comb-shaped polymer, a cationic polymer with improved high-temperature stability, and swellable microparticles. Improved surfactants for surfactant and ASP flooding also were presented. Surfactant performance can be optimized by proper selection of hydrocarbon-chain length, branched hydrophobe, and surfactant head group (including benzene sulfonates, propoxylated sulfates, betaines, or sulfobetaines). The pros and cons of molecular modeling were discussed when identifying new EOR surfactants.

Chemical-flood simulation was covered in Session 3. Chemical-flooding simulators developed in China include a number of new physical mechanisms for polymer and ASP flooding. Continuous development of the U. of Texas Chemical Compositional Simulator over the last 30 years allowed implementation and laboratory/field validation of a suite of process model options and led to the development of a new chemical simulator, General Purpose Adaptive Simulator, at the U. of Texas at Austin. The Research Inst. of Petroleum E&P described its development of a well-designed geologic modeling technology to meet precise EOR reservoir-description needs. While the need to employ simplified models for quick evaluation of potential chemical-flood projects was widely recognized, a step-by-step simulation approach, as described for the Minas S/P implementation, is a realistic course for a successful field implementation.