James Lime Play

Introduction

The James Lime is one of the world’s greatest source rocks and reservoirs, generally producing from rudistid (Cretaceous clams) reefs. There is a region in the East Texas Basin where this zone is composed of chalky limestone (Figure 1). This chalk has fairly high porosity but very low permeability (transmissibility) in most cases, unless the rock has natural fractures.

"Much of the James Lime play remains prospective for new drilling."

Because of the fractured nature of chalks, they make excellent horizontal drilling candidates. The first horizontal James well was drilled in 1993 by Union Pacific Resources, but it did not take off as a play until prices improved in 1997.

Today there are over 100 horizontal wells in the James Lime play in Texas and Louisiana, and much area still remains prospective for new drilling. Energy Frontiers Partners (EFP) has one core prospect and many other lead areas to pursue within the play. In addition, EFP has generated maps over the entire play area.

One of the risks associated with the play has been in the production of water in some fracture sets, or the increase in water over time. There is no bottom water drive; however, there is a change in relative permeability of water to gas as the reservoir pressure declines in some areas. This problem occurs in and around Huxley Field . There are some areas where water is not a risk, but the flip side to this fact is that the wells, to date, are not as strong as the areas that carry some water risk. These areas tend to have lower permeability, which can be managed with good completion practices, such as hydraulic fracturing treatment coupled with horizontal drain holes. Most of these wells are located within the western portion of the play south of Trawick Field. Some operators are already showing success with the fracture treatment of older horizontal wells. (See Figure 2 for locations of Huxley, Trawick, and Carthage fields.)

Mapping the fairway of the trend is not difficult, and it requires no seismic. It does require an understanding of the petrophysical properties governing production and what parameters to map. Good mapping begins with production EURs (Estimated Ultimate Recoveries) tied to simple log parameters.

To summarize, the key features to keep in mind about this play are:

  • A relatively easy trend to map.
  • Advent of hydraulic fracs and increased productivity of both old and new wells.
  • The presence of natural fractures gives higher permeability.
  • The average James Lime well on the west side of the play will ultimately yield about 1.2 BCFGE, making the play economic under almost any price scenario. A well ultimately yields about 49% IROR with $4.25 gas.