SBIR-STTR Award

Improved recovery of oil and gas from mature domestic fields depends on the detailed characterization of reservoir structure and continuity. Crosswell seismic is a new technology that addresses this need by allowing the generation of reservoir images showing a level of detail at least ten times higher than what can be achieved with standard surface seismic methods. Although the promise of crosswell seismic has already been demonstrated, full realization of its potential depends on the ability of the data processing methods and algorithms to handle the real-world complexities. In particular, current crosswell data processing algorithms operate under the simplifying assumptions that the wells are vertical, or only slightly deviated, and that the geologic layers are nearly horizontal (not significantly dipping). The objective of the work in this project is to overcome these restricting assumptions by extending to three dimensions the basic crosswell imaging algorithms (traveltime tomography and reflection imaging). This will be achieved by generalizing the methods of tracing seismic rays from sources to receivers so that they work accurately and effectively, even for cases of significantly deviated wells and large structural dips, and then by making modifications to the tomography and reflection imaging algorithms to take advantage of the improved ray tracing functionality. In Phase I, the above approach will be implemented and tested for relatively simple geologic models (continuous horizons, no faulting, folding or pinchouts). In Phase II, the algorithms will be further extended so that they remain valid for more complex geologic models, and the focus of the work will shift to the three-dimensional visualization of crosswell results and the use of a combination of deterministic and geostatistical techniques for building reservoir models based on large multi-profile data sets.

Commercial Applications and Other Benefits as described by the awardee:
The software that will be produced from this project will be of value to crosswell service contractors, as well as to geoscientists and engineers interpreting crosswell data. More generally, the technology developed under this project will enable the successful introduction of high-resolution borehole seismics and specifically crosswell seismics to the gas and oil exploitation and exploration marketplace.

Recent advances in data acquisition from oil and for fields have dramatically decreased survey costs, opening up the potential for multiwell, 3-D surveys over large areas of existing reservoirs. Until recently, most crosswell surveys have been performed on a single vertical well pair creating a very limited 2-D cross section between the wells. Most of the imaging algorithms currently in use were developed under the assumption of near-vertical well trajectories with minimal out-of-plane dip. In real-world reservoir geometries, 3-D effects must be incorporated, and this will require performing multiwell surveys. This project will extend crosswell imaging to handle the three dimensional nature of wells and earth models. The extension from a single vertical well pair to 3-D well and survey geometry has revealed imaging issues that were not addressed in the initial development of crosswell technology. A common earth model framework was developed in Phase I using a Chebychev polynomial representation for performing crosswell imaging. Visualization approaches to 3-D well and survey geometries were also developed. Phase II will develop and test 3-D traveltime inversions, 3-D reflection mapping, and 3-D migration. The effort will result in a series of algorithms and software capable of performing crosswell imaging and visualization in real-world, 3-D, multi-profile crosswell data.

Commercial Applications and Other Benefits as described by the awardee:
Practical 3-D crosswell imaging should take crosswell technology from a limited market to widespread use by geoscientists and reservoir engineers. The use of the technology should greatly improve production of oil and gas from domestic reservoirs, increasing reserves, enhancing recovery, and lowering development and production costs.