Growth Drivers of Bakken Oil Well Productivity

E D Attanasi,P A Freeman

doi:10.1007/s11053-019-09559-5

Abstract

This paper identifies the drivers of the phenomenal growth in productivity in hydraulically fractured horizontal oil wells producing from the middle member of the Bakken Formation in North Dakota. The data show a strong underlying spatial component and somewhat weaker temporal component. Drivers of the spatial component are favorable reservoir conditions. The temporal component of well productivity growth is driven by increasing the number of fracture treatments and by increasing the volume of proppant and injection fluids used on a per fracture treatment basis. Random Forest, a nonparametric modeling procedure often applied in the context of machine learning, is used to identify the relative importance of geologic and well completion factors that have driven the growth in Bakken well productivity. The findings of this study suggest that a significant part of the well productivity increases during the period from 2010 to 2015 has been the result of improved well site selection. For the more recent period, that is, from 2015 through 2017, part of the improved well productivity has resulted from substantial increases in the proppant and injection fluids used per stage and per well.

Highlights

The application of horizontal hydraulically fractured wells to produce ‘‘tight’’ oil, that is, oil from lowpermeability geologic formations, has transformed the face of the North American oil industry
According to the U.S Energy Information Administration (USEIA) estimates, the Bakken accounted for just over 11% of total US onshore oil production for 2017 (USEIA 2018), and by the spring of 2019, it had reached nearly 1.4 million barrels per day (1 barrel = 0.159 m3)
Drilling and production of horizontal hydraulically fractured wells have become the standard methods for producing Bakken oil

Summary

INTRODUCTION

The application of horizontal hydraulically fractured wells to produce ‘‘tight’’ oil, that is, oil from lowpermeability geologic formations, has transformed the face of the North American oil industry. Historical data on the characteristics of well and fracture design (volume of injected fluid, proppant used, lateral length) were used along with the predicted oil in place at drilled locations to calibrate a model to estimate the first 12 months of well production to create play-wide productivity maps. These include data from which one can estimate the lateral length, number of fracture stages, and volume of proppant and fracture fluids that were injected as part of the fracture treatments Those wells that had incomplete information were dropped from the analysis leaving about 8345 horizontal hydraulically fractured wells that started production from 2009 through 2017 and produced oil for at least 360 days. Corresponding to the noticeable increase in median, well productivities from 2015 through 2017 (see Fig. 3a–e, except in Fig. 3d the productivity change is very subtle), are a 60% increase in proppant per stage, a 40% increase in injection fluids per stage, and an 18% increase in the number of stages per well

Method of Analysis

Design parameters

Findings

CONCLUSIONS