Breaking Up Is Hard To Do: Creating Hydraulic-Fracture Complexity in the Bakken

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 163827, ’Breaking Up Is Hard To Do: Creating Hydraulic-Fracture Complexity in the Bakken Central Basin,’ by C. Mark Pearson, SPE, Larry Griffin, SPE, and Chris Wright, Liberty Resources, and Leen Weijers, SPE, Liberty Oilfield Services, prepared for the 2013 SPE Hydraulic Fracturing Technology Conference, The Woodlands, Texas, 4-6 February. The paper has not been peer reviewed. Drilling the Bakken in North Dakota has increased dramatically over the past several years as operators sought to hold acreage and create value with the drill bit. Much of this activity has been in the central-basin portion of the Williston basin where wells drilled before 2008 were uneconomic. Advances in completion technology caused a fundamental shift in economics, and the whole central-basin area, greater than 2,500 sq miles, has approximately 100 rigs drilling. The greatest change in completion design was incorporating high-intensity multistage fracturing. The Bakken completion design is different from other shale-gas developments, with the widespread use of uncemented liners with external packers in the openhole lateral to create the multistage zonal isolation. Introduction The Bakken formation (highlighted in red in Fig. 1) is part of the Williston basin, which spans southern Saskatchewan and Manitoba in Canada into North Dakota and Montana in the United States. The basin was formed as a subtle down- warping between the Superior craton to the northeast and the Wyoming craton to the southwest. The Williston basin is a gently dipping basin with very little structural deformation, except for a few structural features including the Nesson anticline and the Cedar Creek anticline, shown in Fig. 1. The Upper and Lower Bakken shales are prolific source rocks for the petroleum system. The middle member consists of five to seven distinct lithofacies that range from silty sandstone on the east flank of the basin to silty dolomite on the west flank. Porosities in the middle member range from 4 to 10%, and permeabilities generally are less than 0.1 md. Development History The first Bakken-formation well came on production in 1953, 2 years after first oil production in North Dakota. Over the next 15 years, a total of 42 vertical wells were completed in the Middle Bakken or Three Forks formations. Commercial production required the existence of natural fractures associated with the uplift and could be correlated to the second- derivative curvature in the formation.