Pressure Responses From Induced Hydraulic Fractures in Adjacent Wells Within a Petroleum Reservoir: An Experiment
Authors: Komar C.A. , Shuck L.Z. 
Published: December 2007

Introduction

Research is currently in progress at the Morgantown Energy Research Center to determine if preferred fracture directions are regional or relatively localized in particular oil fields. As part of the research program, particular oil fields. As part of the research program, experiments were conducted to detect the initiation, location propagation, and lateral extent of induced hydraulic propagation, and lateral extent of induced hydraulic fractures in the oil-productive Bradford Third sandstone formation near Bradford, Pa. Quantitative information on fracture orientation and length would allow accurate planning of well patterns to optimize secondary recovery planning of well patterns to optimize secondary recovery operations and minimize payout time. In particular, this information could be significant in determining the distances needed between wells to connect induced hydraulic fractures for water injection and to increase the lateral distance between injection wells and possibly the number of wells needed to waterflood a property efficiently.

Experimental Approach

The measurement of the fracture position away from the wellbore is the prime target of the current study. Location of the test site with respect to the hydraulically fractured wells is shown in Fig. 1. To establish such a technique and to obtain quantitative evidence of how fractures propagate and how far they extend, the pressure propagate and how far they extend, the pressure disturbances created by induced hydraulic-fracturing operations in five adjacent oil wells were monitored within the same reservoir. Each fracture design used about 10,000 gal of fresh water, 10,000 lb of 20-40 sand, and injection raws of 17 to 20 bbl/min. All fracture operations were performed in the open hole with the use of packers and suitable plug-back arrangements. No casing or packers and suitable plug-back arrangements. No casing or perforations were involved. The monitoring wells were also perforations were involved. The monitoring wells were also open-hole completions. A comparison of the fracture parameters used in the wellbore stimulation treatments is parameters used in the wellbore stimulation treatments is made in Table 1.

During the experiments, pressure responses were recorded before wellbore pressurization, during the fracture-extension phase, and after the fractured well was shut in following stimulation. Pressure readings at each well in the test site were recorded simultaneously at preselected time intervals ranging from 10 seconds to preselected time intervals ranging from 10 seconds to several minutes.

These observed responses were compared with wellbore orientations, as determined by impression packers, and with computer-generated calculations of the created propagating fracture length to interpret the effects propagating fracture length to interpret the effects of fluid injection rate on induced-fracture propagation and extent.

Analyses of sequential contour plots during the stimulation treatments indicated thatcyclic pressure waves were generated during four stages on Wells 1, 2, and 4;step-pressure changes occurred on Well 3; andpressure buildup occurred near Well 5. These events are discussed in the following sections.

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