UNION OIL OF CALIFORNIA
MCKITTRICK FRONT #415
CYMRICK FIELD
KERN COUNTY, CALIFORNIA
LABORATORY REPORT NO. 86-2-93T
BJ TITAN SERVICES REPRESENTATIVE
JAY GARNER
BAKERSFIELD, CALIFORNIA
APRIL 23, 1986
5500 Northwest Central Drive ¥ Houston Texas 77092 ¥ 713-462-4239
Laboratory Report
SUBJECT AND PURPOSE
Analyze core samples from the Antelope/Opal A, Antelope/Opal CT, MacDonald Shale, and the Devil Water Silt formations. Samples were submitted by Union Oil of California from McKittrick Front #415, Cymrick field, Kern County, California.
COMMENTS
Antelope/Opal A
The Antelope/Opal A was found to be predominantly opal-amorphous with quartz, calcite, dolomite, and clays, both migrating and swellable.
The formation has a soft but consolidated matrix with natural fractures. The permeability of this formation is 3.80 md to nitrogen.
Acid solubility of the Opal A at room temperature to 15% hydrochloric acid is 7.5% by weight and to 12:3% HCl:HF is 82.1% by weight.
Core flow study showed that no improvement occurred with acid flow.
The best stimulation for this formation would be hydraulic fracturing with high concentration of large sand (16/20 or 8/12). The fracturing system may be water based with potassium chloride and clay stabilizers.
The Opal A is saturated with crude and needs a solvent treatment before acid can react with formation. Therefore, a good wellbore cleanup system would be a BJ Titan 6% HCl:1% HF One Shot system. Iron chelators should be used within the acid system due to the yellow color noted in immersion test.
Antelope/Opal CT
The Antelope/Opal CT consisted mainly of opal-cristobalite with quartz, calcite, dolomite, and migrating and swellable clays.
The Opal CT appears to have a well consolidated matrix with natural fractures throughout the sample. The matrix permeability to nitrogen is 0.138 md.
Acid solubility at room temperature is 12.3% by weight in 15% hydrochloric acid and 87% by weight in 12 3% HCl:HF.
Hydraulic fracturing would be the best means of stimulation for this formation. The fracturing system may be a water based system containing potassium chloride and clay stabilizing agents.
A good cleanup acid would be 15% hydrochloric acid. This formation is a borderline case for using hydrochloric:hydrofluoric acid. Iron chelators should be used within the acid system due to the presence of siderite.
MacDonald Shale
The MacDonald Shale is predominantly quartz and dolomite with migrating clays and a trace of swellable clays.
The MacDonald Shale has a well consolidated matrix with natural fractures within the formation. The permeability to nitrogen is 0.579 md. Flow studies showed acid to increase permeability.
Acid solubility, at room temperature, to 15% hydrochloric acid is 34.9% by weight and to 12:3% HCl:HF is 82% by weight.
This formation would best be stimulated by a typical hydraulic fracturing treatment. A water based system containing potassium chloride and clay stabilizers may be used as the fracturing system.
Cleanup acid for the MacDonald Shale would be a 15% hydrochloric acid system. Hydrochloric:hydrofluoric acids should not be used on this formation. Iron chelators should be used in acid system due to the presence of siderite.
Devil Water Silt
The Devil Water Silt is similar to the MacDonald Shale and is predominantly quartz and dolomite with migrating clays.
This formation also has a well consolidated matrix with natural fractures. The permeability to nitrogen is 0.0432 md. Core flow studies did not show an increase in permeability to acid.
Hydraulic fracturing is the best means for stimulating the Devil Water Silt. The fracturing system may be water based containing potassium chloride and clay stabilizers.
Acid solubility at room temperature to 15% hydrochloric acid is 42.1% by weight and to 12:3% HCl:HF is 83.1% by weight.
Hydrochloric acid would be the best cleanup acid to use on the Devil Water Silt. No hydrochloric:hydrofluoric acid should be used on this formation. Iron chelators should be used within the acid system due to the presence of siderite.
RESULTS
Acid Solubility
A representative amount of each sample was dried, crushed, weighed, and treated with 100 ml of the respective acid. The solutions were incubated for a period of time at room temperature and then filtered. The insoluble residue was dried and weighed. The acid solubilities were calculated gravimetrically and are listed below:
| Formation |
Depth (ft) |
Percent by Weight 15% HCl |
Solubility 12:1% HCl:HF |
| Antelope/Opal A | 1216.5-17.5 | 7.5 | 82.1 |
| Antelope/Opal CT | 2217.25-18.25 | 12.3 | 87 |
| MacDonald Shale | 3852-53.5 | 34.9 | 82 |
| Devil Water Silt | 4813 - 14.5 | 42.1 | 83.1 |
Porosities
Samples of each formation were broken from the submitted core and extracted to clean. The porosity of each was then measured using the Ruska porometer. The results are as follows:
| Formation |
Depth (ft) |
Porosity (%) |
| Antelope/Opal A | 1216.5-17.5 | 54 |
| Antelope/Opal CT | 2217.25-18.25 | 8.8 |
| MacDonald Shale | 3852-53.5 | 15.7 |
| Devil Water Silt | 4813-14.5 | 9.7 |
Immersion Analysis
A small portion of each sample was placed into various solutions and evacuated to saturate. After a period of time, the samples were visually examined to determine the degree of disassociation that had occurred. The results are listed below:
| Samples | ||||
| Fluids | Opal A | Opal CT | MacDonald | Devil Water |
| Fresh water | MLS | FLS | FLS | MLS |
| 2% KCl | TLS | TLS | TLS | TLS |
| 15% HCl | FLS,YC | FLS,YC | FLS,YC | FLC,YC |
| Kerosene | TLS,DC | TLS,NC | TLS,NC | TLS,SC |
Rock Mechanic Analysis
Cores were taken from the Opal CT, MacDonald Shale, and the Water Silt formations and prepared for Rock Mechanic Analysis. Young's Modulus (E) and Poisson's Ratio (v) were determined on each core. The results are listed below.
| Formation | E (psi) | v (dimensionless) |
| Opal CT | 0.146 x 106 | 0.132 |
| MacDonald | 0.504 x 106 | 0.166 |
| Devil Water | 1.125 x 106 | 0.127 |
Note: Data was obtained using unconfined axial loading. The Opal A formation was not suitable for testing.
Permeability Evaluation
One inch core plugs were drilled from each formation and extracted to clean. The plugs were then prepared and placed into a core testing apparatus where nitrogen permeability was determined. Once the nitrogen permeability was determined, the pluas were saturated with a base fluid (2% KCl) and a fluid flow study performed. The results are as follows:
| Formation | Fluid | Permeability (md) |
| Opal A | Nitrogen | 3.80 Naturally fractured |
| 2% KCl | 1.49 | |
| 7 1/2% HCl | 1.35 | |
| 2% KCl | 1.36 | |
| Opal CT | Nitrogen | 0.138 |
| 2% KCl | Fractured sample | |
| Macdonald | Nitrogen | 0.579 |
| 2% KCl | 0.265 | |
| 7 1/2% HCl | ----- | |
| 2% KCl | 0.498 | |
| Devil Water | Nitrogen | 0.0432 |
| 2% | 0.0038 | |
| 7 1/2% HCl | ------- Fines generated | |
| 2% KCl | 0.0021 |
A portion of each sample was crushed to a fine powder and examined by X-ray diffraction to determine the concentration of crystalline compounds present. The results are as follows:
All results are reported in percent by weight.
| Opal A | Opal CT | MacDonald | Devil Water | ||
| Compounds | 1216.5-17.5 | 2217.25-18.25 | 3852-53.5 | 4813.14.5 | |
| Quartz | 10 | 12 | 40 | 40 | |
| Opal-A $ | 50-60 | ND | ND | ND | |
| Opal CT + | ND | 30-40 | ND | ND | |
| Plagioclase | 3 | 3 | <1 | 1 | |
| K-Feldspar | ND | 5 | 1 | 1 | |
| Calcite | 6 | 12 | 45 | 40 | |
| Dolomite | 2 | 2 | TR | 4 | |
| Siderite | ND | 4 | TR | 3 | |
| Pyrite | 4 | 5 | 5 | 6 | |
| Apatite | ND | TR | TR | TR | |
| Mica/Illite | 2 | 3 | 2 | 1 | |
| Kaolinite | 2 | 3 | 5 | 3 | |
| Illite-Smectite | ND | ND | ND | ND | |
| Smectite | <l0 | <10 | TR | ND |
Reference Opal A and Opal CT -
Above abundance estimates are based on XRD measurements and visual estimate of the mineral phases in thin sections.
Reference MacDonald Shale -
Sample may contain amorphous or poorly crystallized opal-cristobalite not detected by XRD.
Reference Devil Water Silt -
A <2 micron clay fraction was not separated from the bulk sample. The above abundance estimates are based entirely on XRD measurements made on the bulk sample.
Scanning Electron Micrographic Evaluation (SEM)
[Figures 11-4 go here.]
Report #86-2-93T
Requested by: Jay Garner
Location: Bakersfield, CA
Analyzed by: GB, JB, JRW
Distribution: Unical Oil, J. Garner, D. Bilden, Lab (2)
86293T/et