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Abstract: Discovery and Development of the Person Field, Karnes County, Texas*
*Paper presented before the Society, May 9, 1960.
Person Field is significant principally because it has proven the presence of oil accumulation in commercial quantities in the downdip portion of the Edwards trend.
The field is similar to other well known Edwards limestone fields of south Texas in that it produces on the upthrown side of a north dipping fault which faults the upper Edwards against the impervious Georgetown limestone. The productive section in the Person Field consists of the upper 200-350 feet of the Edwards. This section is characterized by streaks of porous limestone with considerable fracturing and vugular to intergranular porosity separated by sections of hard dense limestone with no measurable porosity or permeability. Three productive sections tested in the discovery well had average porosities of 11- 13 percent and average permeabilities of 11- 12 millidarcies. A definite gas-cap has been established approximately 200 feet thick. The oil column appears to have a thickness of 100 to 150 feet. With the existence of the thick gas-cap, high-ratio problems have been fairly common and thus have complicated completions.
The field is still in the process of development and the limits have not been defined; however, as this paper is written the field extends 4 miles in a northeast-southwest direction and approximately 1 to 1½ miles in a northwest- southeast direction. Sixteen wells have been completed, three wells are drilling and one is testing. The 16 producing wells have a total daily maximum allowable of 4550 barrels per producing day. The field is presently producing under upper Edwards field rules set by the Railroad Commission providing for 330/1320 foot spacing, 80 acre oil proration units, plus 40 acre tolerance for the last well on a lease, an allocation formula of 75 percent acreage and 25 percent per well. The net oil-gas ratio is 2000-1. Permission was also granted to form 640 acre producing units, in which not more than one-half of the wells may be shut-in.
Unnumbered Figure. Location Map, Person Field, Karnes County, Texas.
Unnumbered Figure. Structure Map, Person Field, Karnes County, Texas.