Crosswell electromagnetic and seismic imaging: An examination of coincident surveys at a steam flood project

Abstract

We studied crosswell electromagnetic and seismic images of three oil‐saturated intervals within a southern California heavy oil field undergoing steam flood. The crosswell survey is located in a portion of the field where one well is in a “cold spot,” resulting in differing steam propagation within the three units. Log analysis shows linear or second‐order polynomial relationships (with correlation coefficients greater than 0.7) between electrical conductivity and water saturation, porosity, and clay content; whereas only a weakly linear relationship can be found between velocity and temperature in the lower unit studied. Crosswell seismic data is used to produce a velocity tomogram and a reflection section, and crosswell electromagnetic data is used to produce a conductivity section and derived porosity and water saturation. The seismic velocities from the tomograms show lateral variations consistent with the lateral variations in temperature seen in observation wells on either side of the crosswell section. The continuity and disruption of seismic reflections coincide with zones of continuous and variable porosity and water saturation as produced from the crosswell electromagnetic inverted conductivity section, and the derived regression fits between conductivity and porosity/water saturation. Seismic velocities, reflections, electrical conductivity, and the derived porosity and water saturation sections all contribute to explaining the observed lateral temperature variations between the wells within the three reservoir units. The unit with high steam content has low water saturation, high porosity, and laterally continuous low‐velocity and seismic reflections, consistent with no barriers to flow. The upper unit, where steam breaks through later in the experiment, also has high porosity and laterally continuous seismic reflections. However, it shows a velocity gradient between the hot and cold wells consistent with the lack of steam in the cold well at the time of the experiment. The middle unit, in which steam never reaches the cold well during the experiment, has the highest water saturation and the largest zone of reduced porosity and disrupted seismic reflections, indicating a possible barrierto flow.

Reducing Risk in Basin Scale CO2Sequestration: A Framework for Integrated Monitoring Design

“…Hoversten et al combined coincident high resolution crosswell seismic, electromagnetic surveys and well logs to monitor a CO 2 flood in Lost Hills, California. The presence of three distinct reservoir fluids made interpretation of individual surveys challenging.…”

Sensitivity study of borehole-to-surface and crosswell electromagnetic measurements acquired with energized steel casing to water displacement in hydrocarbon-bearing layers

“…This paper describes a model study to investigate the possibility of using steel casing as an electromagnetic (EM) source to detect and quantify oil-saturated formations and to estimate time-lapse variations of electrical resistivity due to fluid movement in an active hydrocarbon reservoir. Complementary experimental results in this area of research can be found in Kirkendall et al (1999), Hoversten et al (1995), and Bevc and Morrison (1991). In this work, we employ a numerical method to simulate cross-well and borehole-to-surface EM measurements in the presence of cased wells.…”

Application of 2.5D cross-hole electromagnetic inversion in Gudao Oil Field, East China

“…Wilt et al (1995Wilt et al ( , 1997 reported on the application of crosswell EM in steamflood monitoring. Hoversten et al (2004) introduced an examination of coincident surveys of crosswell electromagnetic and seismic imaging at a steam flood project and demonstrated the sensitivity of the two techniques to different reservoir parameters. In 1997, Shengli oil field in East China, in cooperation with the EMI Company, carried out a large scale pilot test of cross-hole EM measurement.…”