Abstract: New Oil from an Old Oil Field: Results of Redevelopment from Platform Hogan, Carpinteria Offshore Field, California

EDWARDS, EDWIN, Pacific Operators Offshore, Inc.

Platform Hogan is located on Federal lease OCS-P 0166 in the Carpinteria Offshore oil field near Santa Barbara, California. The field was discovered by Chevron in 1964 and ultimately was found to include portions of 2 Federal leases and 3 State of California leases. Platforms Hogan and Houchin were installed in 1968. Platform Hogan reached peak production of 11,691 barrels per day from 31 wells in mid-1969. The field produces from multiple sand zones of Repettian (lower Pliocene) age, trapped in a faulted anticline. Signal Hill Service, Inc. obtained Platforms Hogan and Houchin from Phillips Petroleum in 1990, when Hogan production had declined to 500 barrels per day, and established Pacific Operators Offshore, Inc. (POOI) as operator. With an estimated 6 year economic life remaining, POOI entered two Department of Energy (DOE) programs: the Advanced Reservoir Management (ARM) project, a cooperative study with Los Alamos National Laboratory, University of Southern California and others, to develop a detailed geologic and reservoir characterization of the field, and a DOE Class III grant program to provide cost sharing for drilling to test the feasibility of field re-development using horizontal drilling.

The ARM project studies resulted in a field wide re-correlation and unification of zone terminology leading to the construction of field wide structure maps for each zone. A 3-D geologic model was made which permitted visualization of structure in relationship to existing well paths. Faulting was re-evaluated using detailed well log correlation and by mapping oil saturation patterns in each of the 29 recognized zones.

In preparation for drilling the Class III well, additional detailed geologic and reservoir studies were undertaken and Platform Hogan was selected as the site for the demonstration drilling program. Drilling prospects reachable by redrills from existing Hogan wells were evaluated and ranked. Comingled production made estimation of remaining zone saturations difficult, so pilot wells in each target fault block were required. These near-vertical pilot wells, which were completed as producers, proved critical to the success of the project. Horizontal redrills were planned into individual zones with the best remaining saturation as evidenced by the pilot wells. Preliminary well trajectory layout was done with the help of the 3-D model to establish paths to the targets with acceptable dogleg while avoiding the multitude of existing wellbores. The horizontal portion of the well courses were planned to take a catenary-like path through their respective target zones in order to intersect all stratigraphic elements of the internally layered turbidite sands.

In all, 2 pilot wells and 4 horizontal wells were drilled in the first phase of re-development. All 6 wells were drilled in 5 months as 6 1/8 inch redrills from existing cased wellbores. The horizontals were guided and logged using Measurement While Drilling (MWD) techniques. In sum, this first re-development phase added 743 net barrels per day of incremental oil production to Platform Hogan. Initial phase drilling results coupled with the ARM and Class III studies indicate the likely presence of numerous similar re-development opportunities still remaining in Carpinteria field.

AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California