LAS ANIMAS EXPLORATORY DRILLING STRONG, OIL PRODUCTION INCREASING

Union Pacific Resources Co., Fort Worth, and Sinclair Oil Corp., Salt Lake City, have kicked off a multiwell exploration/development program along the Las Animas arch in southeastern Colorado.

UPRC's activities have grown markedly in the area during the 1980s, owing largely to mineral rights attached to its checkerboarded land position along Union Pacific Railroad right-of-way.

The company has drilled a few wells off the right of way, and several wells in the program with Sinclair also will be outside it.

UPRC's southeastern Colorado operated oil production averaged 11,400 b/d during June 1991, compared with 1,100 b/d in mid-1980. The present figure is an estimated 15% of the state's oil production.

The company operates 180 producing wells and gas processing plants in Bledsoe Ranch, Frontera, and Mount Pearl fields in the area, about 150 miles southeast of Denver. It has submitted an authorization for expenditures to partners for another plant in Arapahoe unit.

The program's first well, 1 Esther, in 22-12s-43w, 25 miles south of Burlington in Kit Carson County, was a dry hole. So was 1 Temple, in 21 16s-47w, Cheyenne County, despite an encouraging Mississippian Spergen interval that drillstem tested wet.

The 1 Keller, in 36-17s-42w, and 1 Montauk, in 7-17s-46w, both in Kiowa County, were drilling in early August.

The overall Morrow play has helped boost Colorado's crude oil reserves to 359 million bbl at the end of 1989 from 198 million bbl at the yearend 1985.

JOINT VENTURE GOALS

Aim of the 50-50 joint venture is to pursue the productivity of the Pennsylvanian Morrow sandstone in the region.

The partners plan to drill 50 exploratory wells at a cost of about $5 million during the first 15 months of the 3 year program. They will use the remaining 21 months to drill follow-up wells to develop any discoveries.

UPRC will operate all of the joint venture wells and properties. Closely held Sinclair is a large gasoline marketer in the Rocky Mountains and operates refineries in Wyoming and Oklahoma.

Lands dedicated to the joint venture are in Cheyenne, Kiowa, Kit Carson, and Lincoln counties, Colo.

Morrow in the area lies at 5,100-6,200 ft, and wells can be drilled in a week. Well costs are about $100,000 for a dry hole and $250,000 for a producer.

Other than the two rigs running for the joint venture, UPRC is running one rig that has about six development wells to drill. Therefore, the UPRC-Sinclair joint venture represents the continuation of UPRC's activity rather than an addition to the play.

LAS ANIMAS BUSY

UPRC notes that seven secondary recovery units have been formed in the area for gas or water injection, which can increase reserves by more than 50% above expected primary recovery. UPRC operates four of the units.

Arapahoe Unit has 62 wells and under gas pressure maintenance is producing a gross 4,000 b/d of highly asphaltic and paraffinic crude that plugs perforations, especially as pressure drops in the high permeability reservoir.

UPRC believes it has begun to see the repressuring effects of gas injection in the unit. It also has had good success reperforating some of the initial completions, usually in the original interval or adding 1-2 ft.

The reworked wells have 12 shots/ft, compared with four shots on the initial completion.

New wells are now completed with eight shots/ft.

In Mount Pearl Unit, where has injection has been in progress much longer, UPRC is still trying to determine the optimum injection scheme and rates.

UPRC also has eliminated hot oiling down the casingtubing annulus, which appears to have done more harm than good to the formation. The company is also considering use of purchased or makeup gas in several units to improve ultimate oil recovery.

UPRC said it has been able to keep good roustabout crews but has had trouble getting and retaining good contract personnel in the remote area. Turnover on rig crews has been high, for example.

TREND DEVELOPMENTS

Various operators are negotiating to form two more units in the Stateline trend of eastern Cheyenne County along the Kansas line.

Those are Second Wind and the tentatively named Northwest Arapahoe unit.

Units on the trend typically employ gas injection for pressure maintenance.

Development drilling is steady in the Speaker field area north of Bledsoe Ranch field near the trend's western end, but it is too early to tell about unitization possibilities there.

Mount Pearl unit has 27 wells producing a gross 3,000 b/d. Frontera field has 21 wells making about 1,000 b/d, and Bledsoe Ranch 15 wells flowing 550 b/d. Second Wind field has about 15 producing wells and is still being developed.

Through Dec. 28, 1990, all operators reported completion of 61 new field wildcats during the year in the Las Animas arch province.

That made the 10,542 sq mile area the second most densely explored province in the U.S. last year in terms of new field wildcats per square mile, Petroleum Information Corp. reported.

By yearend 1990, operators reported completing 169 wells of all types in the province during the year, including six oil discoveries and 11 new pool discoveries or extensions of existing fields.

Besides UPRC/Sinclair, Mull Drilling Co., Anschutz Corp., and numerous other independent operators are active in the region.

Copyright 1991 Oil & Gas Journal. All Rights Reserved.