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Abstract


 
Chapter from: SG 42:  Applications of Previous Hit3-DNext Hit Seismic Data to Exploration and Production

Edited by: 
Paul Weimer and Thomas L. David

Author:
Mike Burnett



Published 1996 as part of Studies in Geology 42
Copyright © 1996 The American Association of Petroleum Geologists.  All Rights Reserved.

*Editorial Note: Page numbers in this digital version (HTML and PDF) do not correspond to those of the hardcopy.
Otherwise, the two are the same.
 

CHAPTER 5

Chapter 5: Previous Hit3-DNext Hit Seismic Expression of a Shallow Fluvial System in West Central Texas

Mike Burnett*

 Burnett, M., Previous Hit3-DNext Hit Seismic expression of a shallow fluvial system in West Central Texas, in P. Weimer and T. L. Davis, eds., AAPG Studies in Geology No. 42 and SEG Previous Hit3-DNext Hit Geophysical Developments Series No. 5, AAPG/SEG, Tulsa, p. 45-56.
Mississippian Lime at approximately 5300 ft (1615 m), the Caddo Lime at 5000 ft (1525 m), the Strawn sand at 4500 ft (1372 m), and the lower Canyon-age Palo Pinto reef at 3000 ft (915 m) (Figure 2). Two wells producing from the Mississippian strata within 2 mi (3.2 km) have a combined cumulative production of 650,000 BO, and the Caddo, Strawn, and Palo Pinto have added more than 5 MMBO from 20-30 more wells. The nearest shallow pay is encountered in Gunsight sands of the Cisco series approximately 
7 mi (11.2 km) to the south.

A 14-mi2 (36-km2) Previous Hit3-DNext Hit program was acquired in eastern Baylor County, Texas, during the fall of 1992. This program was designed to image Canyon, Strawn, and Mississippian objectives. These horizons have all produced oil in the area, and the Previous Hit3-DNext Hit survey was designed to enhance further exploration potential in these horizons.

However, the focus of this paper is on a Pennsylvanian (Cisco age) unit much shallower in the section, this unit being responsible for significant production in Concho County, at the southern end of the Eastern Shelf. The location of the Previous Hit3-DNext Hit survey coincides with a Cisco fluvial system studied by Brown et al. (1990). The Previous Hit3-DNext Hit survey provides evidence of an additional relative lowstand in sea level that occurred early during deposition of this unit. A well was subsequently drilled expressly to test this newly identified unit. Excellent agreement was found between the resulting log and the geology indicated by the Previous Hit3-DNext Hit data. This survey appears to show details of a fluvial channel system including point bars, mid-channel bars, levees, and flood deposits.

Previous Hit3-DNext Hit SURVEY PARAMETERS

In the late summer of 1992, a group of mineral owners and option holders agreed to a joint shoot of 8000 acres in eastern Baylor County. A program was designed for a high-resolution survey with the parameters listed in Table 1.
ABSTRACT

Previous Hit3-DNext Hit surveys have proven to be a powerful structural risk reducer for oilmen in West Central Texas. While the biggest structures were found using single-fold and 2-D common depth point (CDP) shooting, the success rate for stepout Mississippian and Canyon reefs drilled on Previous Hit3-DNext Hit surveys has increased substantially in this area: Previous Hit3-DNext Hit surveys have gained wide acceptance by the oil community in North and West Central Texas.

Whereas 2-D has been relatively ineffective in stratigraphic situations, this paper will showcase a Previous Hit3-DNext Hit survey which was used as a tool to pinpoint a shallow 1500-ft (460-m) meandering channel in the upper Pennsylvanian Cisco system.

Regional studies report evidence of a lowstand of sea-level for this formation, locally called the King, which occurred near the end of deposition (Brown et al., 1990). The Previous Hit3-DNext Hit data appear to demonstrate the presence of another relative lowstand of sea level, which occurred early during deposition of this formation.

Significant detail can apparently be seen in these data, including point bars, levees, and overbank deposits. The data appear to correlate with all logs that penetrate the Previous Hit3-DNext Hit volume: i.e., where a well penetrates the channel location depicted in the seismic image, the logs show evidence of a channel.

This Previous Hit3-DNext Hit survey was designed for objectives at 3000-6000 ft (425-1830 m). Because of this, the fold at the shallow fluvial unit is quite low (three- to four-fold). Additionally, the calculated bandwidth of the data is extremely high, in the 200 Hz and greater range. These data were acquired with an I/O II system and deep-hole dynamite, illustrating the increase in resolution available with modern 24-bit systems.

Because an oil show was reported in this zone during drilling for a deeper objective, a well was drilled to test a point bar identified in the Previous Hit3-DTop data. Although no oil was found, an excellent point bar was encountered, which further authenticated the seismic survey's ability to provide stratigraphic detail about this shallow fluvial unit. This is significant, because most of the oil remaining to be found in this and other areas will come from stratigraphic traps.

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