Print this pageHorizontal Wells in a Clastic Oil Field with Intraformational Compaction
CLARKE, DONALD D., CHRISTOPHER C. PHILLIPS, and LINJI Y
Reservoir characterization of the Tar zone, Fault Block II of the giant Wilmington oil field in Long Beach, CA was performed as part of a DOE cost share project for a steam flood expansion. Similar work is underway in Fault Block V. The geological data was modeled and nine horizontal wells were drilled. It was discovered that the intraformational compaction caused numerous structural misties that could adversely affect the horizontal placement. This problem could negatively impact most unconsolidated sandstone reservoirs in the United States.
In Fault Block II over 700 wells dating back as far as 1937 were used for the study. It was discovered that the newer wells did not match the structure as defined by the older wells. The fifteen foot horizontal well target windows required precision placement. Subsidence over time was evaluated for significant variables because every year the well pad is at a lower elevation. Intraformational compaction over time changes both the depth from the surface and the thickness of the formation. Corrections were made and the horizontal well targets were successfully drilled.
Computer mapping software was used to model the Tar zone in detail and also as a tool to find data busts. An analysis of the problem data revealed that data from wells of the same vintage were compatible but wells of differing ages were not. The data was corrected and the software was used to rapidly produce a new model. For geosteering cross sections of the deterministic model were scaled and graphically enhanced to match the logs and surveys produced by measurement while drilling and logging while drilling. Excellent communication between the geologist and drilling engineer permitted drilling rates of up to 600 feet per hour.