In-Situ Combustion in the Tulare Formation, South Belridge Field, Kern County, California
Authors: Gates C.F. , Jung K.D. , Surface R.A. 
Published: December 2007

Results of the South Belridge Thermal Recovery Experiment indicate the importance of gravity drainage during in-situ combustion in high-permeability, heavy-oil reservoirs. A correlation between sand volume burned and oil displaced is presented for designing and monitoring the process. Substantial oil is recovered from the unburned sand below the process. Substantial oil is recovered from the unburned sand below the burned volume.

Introduction
The in-situ combustion method of oil recovery was undertaken first in 1956 in the South Belridge Thermal Recovery Experiment of the Tulare formation. This field research was based on prior work and supported by 12 oil companies. Results through 1957 were presented by Gates and Ramey. In-situ combustion in the experiment continued for 2 years more. Additional performance data and coring in Nov. 1959 provided further analysis and interpretation of results. Oil produced was 56.7 percent of the oil in place in the total burned area at the start of combustion. A set of design curves was prepared that may be used for engineering and economic appraisals of commercial recovery of heavy oil by in-situ combustion in reservoirs with similar characteristics. Case histories of other in-situ combustion projects in California have been reported in the literature . A screening guide for fireflood prospects was presented by Chu.
In 1964 a more extensive field application of the in-situ combustion method began in the D and E sands of the Tulare formation on the southeast nose of South Belridge field in Section 12. Performance to date conforms well with design curves. Total oil recovery is 6.4 million bbl or 22.3 percent of the original oil in place, about twice the expected primary ultimate recovery. The oil rate remains at the highest level yet achieved.

South Belridge Field
The over-all structure of the South Belridge field at the Tulare formation is a northwest-southeast trending anticline about 9 x 2 miles, with sands deposited halo-like around the flanks and with shaly sands across the axial portion. Locations of the South Belridge Thermal portion. Locations of the South Belridge Thermal Recovery Experiment and Section 12 In-Situ Combustion Project on Mobil Oil Corp's portion of the field are Project on Mobil Oil Corp's portion of the field are shown in Fig. 1.

South Belridge Thermal Recovery Experiment
The South Belridge Thermal Recovery Experiment was located in the Tulare B zone at 700 ft. Locations of all wells involved are shown in Fig. 2. Spontaneous ignition occurred in June 1956. Core Holes 2 through 4 were drilled in Nov. 1957 and Core Holes 5 through 12 were drilled in Nov. 1959 to determine the vertical thickness burned and the reduction in oil saturation in the test pattern and adjacent area. pattern and adjacent area. The average reservoir properties determined from all data available after the Nov. 1959 coring are shown in Table 1. In-place porosity of 36 percent was estimated from the porosity of coke-consolidated cores recovered after combustion.

Burned Thickness
To obtain quantitative data on the burned volume, one punch-Type core was recovered per foot. Burned sand punch-Type core was recovered per foot. Burned sand was identified by its reddish color (rather than gray-blue), absence of oil in the cores, and small amounts of coke in some cores.
JPT
P. 798