Abstract: Improving Recovery from a Diagenetically Complex Carbonate Reservoir: The West Dollarhide Field, Lea County, Southeast New Mexico

JOHNSON, IMELDA G., Dept. of Geosciences, Texas Tech University, Lubbock, TX;JAMES L. BROWN, Texaco E&P, inc., Midland, TX; andGEORGE B. ASQUITH, Department of Geosciences, Texas Tech University, Lubbock, TX.

The West Dollarhide Field in Lea County, New Mexico forms the western extension of the Dollarhide Field in Andrews County, Texas. The Drinkard unit is Middle Leonardian in age, and was deposited along the western flank of the Central Basin Platform. The original pay zone was thought to be more or less continuous throughout the cored interval. However, detailed petrographic analysis of the core has determined that the depositional facies and diagenetic fabrics are more heterogeneous than previously known, and that they are consequently compartmentalizing the reservoir.

The main production is from a paleotopographic high located in the southern portion of the field. In the West Dollarhide Field the Drinkard unit was deposited in a shallow-water inner-ramp depositional setting. Dolomitization within these sediments is associated with either tidal-flat or subtidal deposits. Detailed petrography reveals four distinct 5-10 feet thick coarser crystalline dolomite zones, with an average crystal diameter between 80 150 micrometers, that could be distinguished in each core. It is considered likely that these sediments were dolomitized soon after deposition, as much of the original depositional fabric has been destroyed. There is a marked increase in the measured porosity and permeability in the dolomitized intervals that quickly drops off as crystal diameter decreases. A horizontal well path, that resulted in 2000 feet of lateral extension, targeted the four main coarser dolomite intervals.

The modeling of depositional, diagenetic and petrophysical characteristics of the Drinkard unit provides a better understanding of the dimensions of the compartmentalized reservoir intervals. Within the Drinkard the extent of dolomitization and the high frequency of relative sea level fluctuations are important parameters in a fluid-flow model.

AAPG Search and Discovery Article #90936©1998 AAPG Southwest Section Meeting, Wichita Falls, Texas