Two Successful Steam/Foam Field Tests, Sections 15A and 26C, Midway-Sunset Field
- J.F. Ploeg (Chevron Oil Field Reserach Co.) | J.H. Duerksen (Chevron Oil Field Reserach Co.)
- Document ID
- Society of Petroleum Engineers
- SPE California Regional Meeting, 27-29 March, Bakersfield, California
- Publication Date
- Document Type
- Conference Paper
- 1985. Society of Petroleum Engineers
- 5.1 Reservoir Characterisation, 1.10 Drilling Equipment, 2.5.2 Fracturing Materials (Fluids, Proppant), 5.4.2 Gas Injection Methods, 5.3.2 Multiphase Flow, 2.4.3 Sand/Solids Control, 4.1.5 Processing Equipment, 5.4.6 Thermal Methods, 5.3.4 Reduction of Residual Oil Saturation, 4.1.2 Separation and Treating, 5.2.1 Phase Behavior and PVT Measurements, 5.8.5 Oil Sand, Oil Shale, Bitumen, 2.7.1 Completion Fluids, 4.2 Pipelines, Flowlines and Risers
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Two successful steam-diverting field tests were conducted at the Midway-Sunset Field in the Joaquin Valley, California. A Chevron proprietary sulfonate was used as a steam-diverting agent to improve oil recovery. The results showed that, for the conditions of the field experiment, the sulfonate used is very economic, significantly increasing oil recovery. Also, there were no associated sulfonate-handling and produced oil-treating problems. problems.
Since the introduction of steam injection in the late fifties, this technique has become the most successful enhanced oil recovery (EOR) method for improving the recovery of heavy, viscous oils. To date, steam injection accounts for 78% of the total U.S. EOR production, with 358,000 BOPD.
Notwithstanding the economic success of steam injection, it was recognized early that significant amounts of oil are bypassed due to steam, channeling through high permeability sands in the reservoir and/or gravity override of steam due to its low density. To reduce these effects, several approaches have been proposed using auxiliary materials to divert the steam to the unswept areas of the reservoir, and thus improve oil recovery.
Duerksen reported on a laboratory study to develop a steam-foam surfactant for field testing. Over 50 commercial and experimental surfactants were screened for foamability and thermal stability at steamflood conditions. Screening criteria for foamability were based on the pressure drop across a foam generator or across Ottawa and Kern River Field sandpacks. The test variables studied were foam liquid volume fraction, temperature, pressure, brine concentration, nitrogen pressure, brine concentration, nitrogen concentration, surfactant concentration, and foam flow rate.
Major observations and conclusions from the laboratory study were:
1. A static foam in a sandpack degrades rapidly and requires constant regeneration at flowing conditions to effectively maintain its resistance to steam flow.
2. Foam effectiveness is relatively insensitive to foam liquid volume fraction and foam flow rate.
3. A 1% NaCl and 500 ppm CaCl2 brine was detrimental to the foaming effectiveness of four commercial alpha olefin sulfonate (AOS) surfactants.
4. Foamability varies inversely with temperature and directly with nitrogen concentration in the gas phase of the foam.
Chevron's proprietary sulfonates were compared to alkylaryl and alpha olefin sulfonates. Based on good thermal stability, superior foaming performance, significant reduction of steamflood performance, significant reduction of steamflood residual oil saturation, and good solubility characteristics, a Chevron sulfonate was selected for field testing.
The Midway-Sunset Field is located to the southwest of the San Joaquin Valley in California. Section 15A, the first area selected for a field test, is situated near the northern end of the field. The primary reservoir is the Potter sand which is composed of a series of fine distinct lensing sand members separated by shale breaks or tight zones that are believed to be barriers to vertical steam flow. The massive reservoir sand is up to 500 ft thick and dips 20 degrees to the east. Reservoir and fluid characteristics are summarized in Table 1.
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