Abstract

A detailed subsurface geological study of the Canyon series across Jones and Taylor Counties, Texas has led to multiple wildcat discoveries along this trend. Basic subsurface mapping techniques were used simultaneously with the study of electric log characteristics to determine prospective acreage blocks for exploration. The use of 3-D seismic data was then utilized to more accurately evaluate the top of the Canyon Carbonate series along this trend.

With the use of 3-D seismic, approximately 75 wells have been drilled in this trend from Anson in Jones County, southwest across Taylor County, and into Nolan County. This play is still active, and for that reason exhibits are not presented. This paper will focus on the portion of the trend which crosses Taylor County southwestward into the edge of Nolan County.

The subsurface geological study of the trend area discovered three important aspects that helped the acreage selection process. First, the structural map of the top of the Canyon Carbonate showed productive Canyon Reef features were found generally between 2000 feet down to 2600 feet subsea along the trend. The erratic structural nature of the Canyon Carbonate combined with sometimes very few well penetrations led to the decision to use 3-D seismic data to accurately define the Canyon Carbonate. Secondly, subsurface structural mapping of the shallow horizons also showed drape of these Permian-aged sands and carbonates over the Pennsylvanian aged reefs. It was also noted that numerous shallow Permian-aged features set up by the deeper Canyon reefs had very few penetrations into the Canyon section. Thirdly, the presence of a Canyon Carbonate shelf edge that paralleled the productive Canyon Reef trend was noted. The shelf edge or build-up is generally from 2200 feet up to 1800 feet subsea, some 300 to 400 feet of added section. It was discovered after 3-D shooting that the majority of all the Canyon Carbonate features discovered fell into a two mile window down-dip from the shelf edge which parallels the productive Canyon Reef trend.

A total of 65 square miles of 3-D seismic data was acquired in two continuous projects. As many as 75 different Canyon Reefs have been identified from the seismic data. To date, 33 locations have been drilled completing 23 as Canyon Reef producers for a 70 percent success ratio. The identified prospects all have subsea top between 2200 feet to 2600 feet subsea and occur approximately within the two mile window down dip from the referenced Canyon shelf edge. The majority of the features drilled are structural in nature with four-way closure, while a few successfully drilled features appear to be more stratigraphic in nature. The shallow horizons mapped using the 3-D data confirm they are draped over the deeper Canyon-aged features. Six Canyon drilled locations have yielded secondary payzone discoveries while drilling for the primary 3-D target, the Canyon Reef.

Detailed subsurface geological research is essential. Combined with the use of 3-D seismic data to help define detail beyond imagination, the potential for a major successful exploration project is excellent.