Multiple gas pay zones are easing the economics for operators in a growing gas play in the Deep Bossier formation in southern East Texas.
Early drilling has established Deep Bossier gas productivity along a 7-mile trend on 50,000 gross acres in Leon and Robertson counties held by Gastar Exploration Ltd., Houston. Burlington Resources Inc., Houston, is working the Deep Bossier in the Savell field area to the west in Robertson County (OGJ Online, May 11, 2005).
Wells drilled since October 2004 by Gastar and affiliates Geostar Corp. and First Texas Gas LP have encountered gas pay in several deep Jurassic Bossier intervals, and more recent wells have found net pay in shallower Cretaceous Travis Peak and Pettet.
The earlier wells went to 19,000-20,000 ft and cost $12-13 million/well, but the next well to go on production likely will come in under $10 million at 17,800 ft, said Gastar Pres. and Chief Executive Officer J. Russell Porter.
Drilling depths should relax to 17,500 ft on a good portion of the acreage, and Porter said Gastar is looking toward Bossier-only recoverables of roughly 6 bcf in wells with 1-2 pays and 8-10 bcf in wells with 3-4 pays.
Gastar has room for more than 200 wells if spacing settles at its anticipated 160 acres, Porter added. The company has encountered flowing tubing pressures greater than 10,000 psi.
Gastar, which acquired Geostar’s interests this month, and Burlington Resources are the only players drilling, but others are accumulating acreage, Porter said. A 50 to 60-sq-mile 3D seismic survey will start soon in the two counties. The play surrounds Hilltop, about 25 miles north of Bryan.
Deep Bossier wells
Gastar’s first brush with the play was an interest in a well Anadarko Petroleum Corp. operated in 2001.
Drilled to 21,000 ft, it found gas in the Deep Bossier but didn’t produce due to mechanical problems. Now Gastar operates two rigs and plans to turn its fourth Bossier completion to production in late July.
Gastar set intermediate casing at 11,000 ft after its most recent well, Donelson-1, found apparently commercial gas shows in Pettet at 10,200 ft. The well hasn’t reached Bossier yet but offsets the Tipco Lanier-1, an early 1980s Bossier gas producer.
The first success, Fridkin-Kaufman-1, found 136 ft of net Bossier pay, stabilized at 13 MMcfd, and sold 1.4 bcf of gas by February 2005. TD is 20,050 ft.
Cheney-1, TD 19,150 ft, cut 167 ft of net Bossier pay. The F-K and Cheney well sites have a combined 40-50 million of gas scrubbing capacity to handle the 4-6% carbon dioxide and minor hydrogen sulfide content from multiple wells.
Lone Oak Ranch-1, on a different fault block, started sales in early June at 7 MMcfd from the Bossier. It was treated with a revised fracture stimulation design.
Greer-1, one half mile from F-K-1, cut 57 ft of Bossier net pay and is to go to sales at end-July.
F-K-2, TD 18,700 ft, to go on line in September following a Bossier completion attempt, cut more than 120 ft of net pay in Cretaceous Travis Peak. It also cut 74 ft of apparent net pay in Deep Bossier Lower K sands below 18,000 ft and 10 ft of Deep Bossier pay at 16,700 ft. F-K-1 encountered the K sands, but they were not effectively fracture stimulated.
The Travis Peak pay indication was based on measured permeability from cores greater than 0.1 md, crossover neutron density porosity greater than 8%, and indicated natural fracturing on logs, Gastar said. ✦