Identification of Potential Sweet-Spots by Integrated Analysis of Core Samples and Conventional Wireline Logs in the Barnett Shale Play

Abstract

Identifying the distribution and location of sweet spots in gas shales is generally critical to field planning because of the need to place horizontal laterals with a high probability of success. In order to quantify the centimeter-scale vertical heterogeneity and identify the most prolific reservoir rock, routine measurements include detailed core analyses. Such high degree of vertical variability makes correlation of point-based core measurements and the average responses of wireline logs tedious and time-consuming. In this work, we merge findings from the core-scale with these conventional log responses in order to provide a framework for rapid identification of key rock-types with quantifiable uncertainty. Earlier researchers, have demonstrated the viability of a statistical approach to identify critical measurements that strongly impact productivity, using approximately 400 core-derived measurements acquired from 3 wells. Our work combines the analyses of a set of conventional wireline logs from 28 wells from the Fort Worth Basin of North central Texas, such as gamma ray, photo electric factor, density, neutron porosity and resistivity, along with core analyses from 3 wells (petrophysical measurements made on 400 core samples) allowed us to regionally recognize different petro-types which were originally identified from the core data. Our studies also provide a set of cutoff values have been identified which can be used for a quick look petrophysical evaluation, such as: Density>2.65 g/cm3 and neutron porosity<8 % or gamma ray<70 API and/or deep resistivity<20 ohm-m and/or photo electric factor>4.5 correspond to a lower quality rock type; otherwise the rock is likely to be of a more productive reservoir quality. Krigged maps of different petro-types indicate that thermal maturity has greater control over the total thickness, on the distribution of the sweet-spots. Distributions of the sweet-spots also follow the similar trend of the thickness of the Lower Barnett. Good correspondence between production data and petro-types enhance the confidence of such rock-typing workflow. The proposed workflow for petro-typing using only the triple combo well-logs has good potential for the delineation of the sweet-spots, when used in combination with the geologic knowledge.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017