Compagnie Generale De Geophysique Research Articles

Characterizing and predicting short term performance for the In Salah Krechba field CCS joint industry project

Abstract In 2006, the CO2ReMoVe project funded by the European Commission was launched with the objectives of developing new and common methodologies and technologies to improve site based R&D for the monitoring, measurement and verification of the injection and storage of CO2 at multiple sites. The In Salah Gas Krechba Field Joint Industry Project has been in operation since 2004 when gas from several fields was put on production. To comply with export regulations, the high content of carbon dioxide (CO2), 1–10% in the produced gas is removed and re-injected down dip from the producing gas horizon, through three horizontal injection wells at approximately 1800 m below surface. Within the framework of CO2ReMoVe, this paper discusses the site characterization and the short term system performance for the In Salah Krechba field. Prior to the injection, the reservoir unit and the seals were characterized. The resulting geological (static) model is consistent with the information obtained from the drilling activities in 2004 and 2005 and from the reprocessed 3D seismic done by Compagnie Generale de Geophysique (CGG) in 2006. A fracture study carried out on information obtained from resistivity and acoustic images available on the Krechba field had shown the existence of an open fracture network oriented along the NE-SW direction parallel to the maximum stress direction. Typically, monitoring data serves as a calibration yardstick for the static model. It was therefore valuable information to detect the CO2 breakthrough at KB-5, a suspended well located 1.7 km away from the KB-502 injector well. Tracer analysis confirmed the CO2 detected at KB-5 came from KB-502. A multi-phase, multi-component compositional simulator specially designed for CO2 sequestration (ECLIPSE 1 300 with the CO2SOL option) was used to simulate and predict the properties of the injected carbon dioxide as well as that of the gas in place (mainly methane) and of the saline aquifer. History matching was used to calibrate the dynamic model by iteratively modifying parameters until a satisfactory match between model results and field measurements was obtained. The resulting dynamic model is used for short term predictions of the behaviour of injected CO2. The history matching parameters are the fracture porosity, permeability and matrix permeability (difficult to measure permeability in a fractured medium). In each iteration, the simulated bottomhole pressures, gas (CO2) injection rates were compared against field data as well as the CO2 breakthrough time at KB-5. Iterations were repeated until a good match was obtained. Predictive simulation results indicate that CO2 would reach the northern part of the gas field in 2010 and would spread out over an area including production wells in 2015, both in the northern (KB-502, KB-503) and the eastern part (KB-501) of the gas field. Although a good match has been obtained in the history matching process, some observed discrepancies could still not be explained only by fluid dynamics. Possibly, the application of coupled fluid flow and geomechanical simulations would aid in explaining the remaining discrepancies.

A Late Dorset Site on Axel Heiberg Island

The territory in the Canadian Arctic Archipelago known to have been occupied by the Dorset people has been extended as a result of the finding of a harpoon head on an old camp site consisting of a number of tent rings, and located about seven metres above sea level, near the east bank of a river connecting Buchanan Lake with Mokka Fjord on the east coast of Axel Heiberg Island. The find was made and reported by Robert F. Barstad of the Calgary office of the Compagnie Generale de Geophysique. The specimen, which is of ivory, belongs to a late period of the Dorset culture and exhibits a number of diagnostic attributes, viz: closed rectangular socket, bifurcated spur, double line-holes and a longitudinal lashing groove from the line-hole to the tip ....

Reply to E. Szaraniec by S. H. Ward

We are grateful to Mr. Szaraniec for expressing interest in our work and for bringing one of his publications to our attention. However, his comments have little bearing on the main theme of the paper nor on the results we presented. We confined our discussion to the Schlumberger array, and we checked our forward solutions with some of those of La Compagnie Generale de Geophysique; correct convergence was assured in all cases tested, and illustrations of correct convergence are contained in the paper. We agree thoroughly with Mr. Szaraniec that convergence to the correct asymptotic value requires careful attention and, hence, since we did not use a perfectly insulating subsurface, we also did not use the asymptote pertinent to that model.

Wide-Line Profiling: ABSTRACT

A technique developed and perfected in France by Compagnie Generale de Geophysique makes it possible to record, process, and interpret reflected events originating from every direction. The field layout is the same as that for conventional, multiple-coverage, seismic-reflection profiling. The only difference is that shot points are placed along oblique lines, so as to obtain several parallel, regularly spaced, depth-point lines. After processing, these lines yield comparable, although not identical, seismic sections, and a computer is able to analyze, by the cross correlation process, the slight shift of reflection events caused by lateral gradients. A complete software was developed and the longitudinal dips, lateral dips, total dips, migration offsets, and time corrections are produced by a Calcomp plotter. The basic document is a section obtained by stacking the individual parallel sections after removing events which do not correlate laterally. The Calcomp displays provide the necessary parameters for migrating all events in three dimensions. Considerable improvement over old methods was provided in tectonically complex areas. In other cases, an apparent unconformity resulted from 2 lateral events of opposite dips, a reflection on a fault plane beyond the seismic line was identified, and good results were obtained using lateral dip criteria in an area where high multiplication had been unsuccessful. The advantage of wide-line profiling is that it expands the multiplication in lateral directions at a small cost increase. The software developed by CGG sorts out the seismic arrivals and provides tools for migration in a true three dimensional space. The wide-line profiling technique has now reached the industrial stage and was used successfully in areas with complex structural geology, such as Spain, France, Italy, Libya, Angola, and Canada. End_of_Article - Last_Page 795------------