Texaco Exploration & Production Inc. (TEPI) has applied new directional drilling capabilities in successful well reentry programs in mature U.S. fields about 1,000 miles apart.
In Aneth field of San Juan County, Utah, the company recently completed the world's first quadrilateral, short radius, horizontal well drilled with articulated downhole motors.
Texaco's F114 Aneth Unit well, a horizontal reentry, flowed 547 b/d of oil and 1,207 b/d of water from layered formations at 5,686-5,768 ft. The flow rate was six times the average of a typical vertical well in the field. The well's four horizontal laterals ranged in length from 927 to 1,697 ft.
On State Lease 340 in Cote Blanche Island field of St. Mary Parish, La., Texaco combined directional drilling technology with 3D seismic imaging capabilities, as well as improved equipment and tools, to complete three wells under a salt dome overhang. The company in late October was producing a combined 2,000 b/d of oil and 21.2 MMcfd of gas from the wells while completing a fourth horizontal reentry and drilling a fifth.
TEPI Pres. Clarence P. Cazalot said applying new technology is a key component of the worldwide plan that enables Texaco to find, develop, and produce oil and gas at the lowest possible cost.
RESULTS AT ANETH
Texaco since late 1994 has drilled 16 laterals out of seven vertical wells in Aneth field, including four water injection wells and three producing wells. The reentry program has added 800 b/d of oil and 480 Mcfd of gas production in the field.
Texaco is evaluating the potential yield from a plan to drill more than 60 additional horizontal wells on the acreage in the next 5 years.
Douglas K. Carriger, TEPI's Denver division manager, said the Texaco unit is expanding the role of horizontal technology to include secondary and tertiary recovery projects.
"Proper placement of horizontal laterals in both producing and injection wells will improve waterflood performance and enhance oil recovery bv increasing sweep efficiency," Carriger said. "Also, multiple short radius laterals, such as in F114 Aneth Unit, penetrate more of the reservoir at a lower cost."
Carriger said using horizontal technology in new ways can increase return on investment and, in turn, shareholder value.
"Reentering existing wells and drilling horizontal laterals instead of new infill vertical wells result in fewer locations, roads, flow lines, and power lines," he said.
Texaco found Aneth field in 1956 and formed the Aneth Unit Sept. 1, 1961. Cumulative production from the unit amounts to 135 million bbl of oil and 114 bcf of gas.
Texaco holds a 68.8% working interest in the unit, with the remainder shared by Chieftain International Inc., Mobil Exploration & Production U.S. Inc., Helbing & Podpechan, Reynolds Metals Co., Medallion Production Co., Marathon Oil Co., and JN Exploration & Production LE
COTE BLANCHE PROGRAM
From a geologic and drilling standpoint, sidetracking the wells in South Louisiana on State Lease 340 represented a challenge because they are near the Cote Blanche Island salt dome. The dome is a large salt structure about 20 miles southeast of New Iberia, La., with previously untapped oil and gas reservoirs under salt overhang.
"The proximity of the existing well-bores to the salt dome required sophisticated drilling techniques," said Robert S. Lane, TEPI onshore division manager. "TEPI's rig operations group used directional drilling expertise to build angles in short distances to encounter productive formations under the salt dome overhang.
"This successful sidetracking of existing vertical wells resulted in substantially reduced drilling costs."
Lane said the Texaco unit continues to identify exploration opportunities in mature fields like Cote Blanche Island. TEPI personnel have a wide range of experience drilling horizontal and directional wells elsewhere in Louisiana, East Texas, the North Sea, and the Gulf of Mexico. Personnel in those regions are applying technologies in ways similar to the reentry program that is rejuvenating Cote Blanche Island field.
The field, in West Cote Blanche Bay of the Atchafalaya basin estuary system, is a 1948 discovery. Texaco holds a 100% working interest in 8,500 acres in the field. The company's cumulative production in the field amounts to more than 91 million bbl of oil and 213 bcf of gas.
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