Petrophysical Evaluation Of The Smackover Formation In East Texas

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Significant amounts of hydrocarbons are produced from dolomite and limestone reservoirs produced from dolomite and limestone reservoirs in the Smackover formation in East Texas. The major contributor of these produced volumes and reserves are the dolomites consisting primarily of oomoldic and sucrosic rock types. The oomoldic rock type is the most significant. Predominant limestone rock type is oolitic Predominant limestone rock type is oolitic grainstone. Porosity development is mainly secondary for all rock types. Electrical and acoustical properties are different for the dolomite and limestone lithologies. The residue hydrocarbon trapping characteristics of reservoir quality rock are high as determined by various techniques. Introduction The hydrocarbon productive Smackover formation of Jurassic age in East Texas has been and will be a prime exploratory objective for a number of years. The geographical area covered by this paper is shown in Figure 1. The Smackover formation is overlain by the Buckner and underlain by the Norphlet, all of Jurassic age. The Smackover pinches out updip to the north and west of the Talco-Mexia Fault line. Hydrocarbon accumulations appear to be limited downdip by the absence of porosity development. Numerous gas-condensate and oil fields have been discovered with the larger being Bryans Mill, New Hope, Como and Northeast Edgewood. The larger fields have been found in a band almost midway between the updip porosity pinchout and downdip limit of porosity development. The standard open hole logging program consists of running the induction-electrical and the acoustical velocity surveys. Additional surveys often utilized are natural gamma-ray, gamma-gamma density, neutron (conventional and contact) and microlog surveys. It has been found that for wells drilled with normal water base muds (density 10.0–10.5 pounds per gallon, 8–10 cc fluid loss and 40–50 pounds per gallon, 8–10 cc fluid loss and 40–50 seconds viscosity), filtrate invasion is quite shallow, usually less than two hole diameters. The first porosity development below the top of the Smackover is normally open hole drill stem tested, particularly in exploratory wells. The objectives of drill stem testing are (1) determine fluid content and (2) rate of fluid production. In order to efficiently exploit these accumulations, the amount and distribution of the hydrocarbons initially present as well as the most efficient method of recovering these hydrocarbons needs to be known. This paper defines some of the petrophysical parameters used to evaluate the Smackover and points out difficulties not yet resolved.