Production Analysis Couples Multivariate Statistical Modeling and Pattern Recognition
Authors: Wilson Adam 
Published: February 2015

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 168628, ’Application of Multivariate Statistical Modeling and Geographic-Information-Systems Pattern-Recognition Analysis to Production Results in the Eagle Ford Formation of South Texas,’ by Randy F. LaFollette, SPE, Ghazal Izadi, SPE, and Ming Zhong, SPE, Baker Hughes, prepared for the 2014 SPE Hydraulic Fracturing Technology Conference, The Woodlands, Texas, USA, 4-6 February. The paper has not been peer reviewed.

Approximately 5,000 horizontal Eagle Ford wells have been completed in south Texas. Still, geologists and engineers question whether their companies are using the most appropriate operating practices. Multivariate statistical analysis of larger data sets offers sound interpretation across larger geographic areas, with the provision that correlations need to be scaled to local conditions. The purpose of this paper is to apply multivariate statistical modeling in conjunction with geographic-information-systems (GIS) pattern-recognition work to the Eagle Ford.

Introduction

With approximately 5,000 horizontal Eagle Ford wells now completed, large sets of public and proprietary data are available for production and completion-/ stimulation-optimization studies. However, the processes of gathering data, quality control, learning what questions to ask of the data sets, and learning how to ask these questions in robust statistical fashion contain many challenges. Data sets involving large well counts contain many variables that are not ideally distributed or have missing or bad values.

This work uses particular data-mining methods, particularly GIS mapping and boosted-tree regression modeling, to attempt to overcome some of the challenges with the available data sets to better understand the effect of key well, completion, and stimulation parameters on productivity and production efficiency.

In this work, the Eagle Ford formation of south Texas was divided into three major producing areas that were subsequently studied with mapping techniques and that were individually modeled by use of boosted trees.

Formation, Study Area, and Goals

The Eagle Ford formation is a Late Cretaceous sedimentary-rock formation that underlies much of south Texas. The rocks are mainly organic-matter-rich fossiliferous marine shales of the Lower Eagle Ford interval. The play extends over an area of approximately 11 million acres overall, and the main body of the play stretches from the Texas/Mexico border to the eastern borders of Gonzales and Lavaca counties (Fig. 1). The northern part of the play (highlighted in green) is in the oil-maturation window, and, in addition to producing crude oil, it also contains lesser amounts of natural gas and natural-gas liquids (NGLs). Situated to the south and southeast of the oil window, the wet-gas region (highlighted in yellow) produces gas along with high volumes of NGLs. The southernmost region (highlighted in red) contains mostly dry natural gas. Because oil and NGLs command a higher price than natural gas, producers have mostly focused on extracting the formation’s oil and NGL resources.