High resolution chemostratigraphy: a new method for geosteering in clastic reservoirs at the wellsite: a case study of a recent well drilled in the TAG-I reservoir in Algeria
Triassic Argilo Gréseux-Inférieur (TAG-I) fluvio-lacustrine sandstones of the Berkine Basin, in Algeria, form a significant hydrocarbon reservoir. These sandstones were deposited by braided, and low to moderately sinuosity fluvial channels, which are concentrated into fluvial fairways separated by floodplains with extensive palaeosol developments. Detailed reservoir-scale sandstone correlation is hampered by marked vertical and lateral facies variations, plus the sequences are biostratigraphically barren. However, chemostratigraphy has produced a four-fold regional zonation for the TAG-I, with a more detailed field-scale zonation. These zonations are based on geochemical variations that reflect changes in provenance and the depositional environment.
During the drilling of a sinusoidal well on the Rhourde Oulad Djemaaa (ROD) Field, real-time geochemical analyses of cuttings were undertaken by laser-induced breakdown spectrometry (LaserStrat®). The resultant geochemical data and the field-scale zonation were then used together to geosteer the well successfully along the optimum prognosed pathway down through the overlying Triassic Carbonate, then guiding the well bore through three passes of the Upper and Middle TAG-I. The geochemical data also enable soil maturity to be determined real-time, so that subsequent wells can be geosteered away from floodplain successions that contained few sandstones. High-resolution chemostratigraphy provides the framework for constraining wellsite deployments and enables wells to be drilled closer to their optimum field development programme.
New Tools, Materials, and Techniques in Intelligent Well Production/Drilling (SPE)
2004 AAPG International Conference and Exhibition Technical Program