James Lime Play
Production Characteristics
The James Lime along the east flank of the East Texas Basin and south side of the Sabine Uplift (Figure 2) is characterized by modest statistical numbers, except at Trawick Field. Trawick is the benchmark “Trype” field for the whole trend and is unique in the high numbers of wells drilled in the James Lime – all of which are vertical. The field has an average Cum of over 2.2 BCFGE (at P65) and high Cum of over 12.7 BCFGE. The median (P50) Cum at Trawick is 1.1 BCFGE. A P10 Cum, or lowest 10% of performers, is about 150 MMCFGE, with the bottom 25th percentile of all Trawick wells yielding at least 467 MMCFGE. These numbers are displayed in Figure 3, a probability distribution plot for the Trawick Field, the non-Trawick vertical gas wells, and the non-Trawick horizontal wells in Nacogdoches County, Texas.
The plot shows that there are only a few old vertical producers outside of Trawick field; yet a number of these wells have been offset with horizontal producers. Prior to the horizontal play developing, the best vertical well was only going to ultimately yield 800 MMCFG. This is in contrast to the fact that the horizontal wells have an average ultimate yield (EUR) of at least 1 BCFG. The best horizontal well is going to yield about 3 BCFG, and 75% of the wells will make at least 500 MMCFG. Therefore, horizontal drilling is definitely helping to prevent a poor well, and even helps to boost the “typical case scenario.” The shape of the best fit line through the horizontal wells, and the fact there are only about 14 wells in the database (perhaps 3 more have been drilled in the area), demonstrates that the probability statistics are incomplete.
Figure 4 shows a log-log plot of practical IP (Best Monthly Cum) versus Cum, and clearly shows a power-law fit to the data, typical of many fractured lime plays. The average and median wells are circled, and the dashed red line is a best fit line for the known fracture stimulated wells, which shows an upward adjustment from the stimulation.
Figure 5, the Samson Lone Star Johnson-Rippy No. 1 horizontal well, demonstrates the play’s type decline curve. It has never been fracture stimulated, but it still represents a slightly better-than-average case scenario for cash flow modeling. The well shows the typical hyperbolic decline curve seen in almost every producing well in the trend. It should be noted that the EUR numbers used in the statistical database were declined on a more conservative exponential decline.
The challenge is to predict how fracture stimulation in the James Lime horizontal wells will affect the ultimate recoveries for these older wells and future wells. A look at the decline histories for some fracture stimulated horizontal wells can serve as a window into the future.