Water-Injection Operations and Gas-Injection Sensitivities in the Bakken Formation

Fig. 1—(a) Top view of the reservoir displaying the location of individual wells and local grid refinement used for building hydraulic fractures along the wells; (b) 3D view of the model.

Although improvement in hydraulic-fracture properties and infill drilling remains the focus of recovery enhancement from the Bakken, low oil recoveries and steep initial decline rates are experienced in primary-recovery operations, even after application of multifractured-horizontal-well technology. Therefore, many pilots have been executed to determine the viability of waterflooding for maintaining oil rates and improving recoveries through reservoir-pressure maintenance and sweep-efficiency enhancement. This paper presents the performance results from one of the waterflood pilots in the Viewfield Bakken. 

Numerical-Model Setup

A section of the Bakken reservoir (the geology of which is described in detail in the complete paper) deemed to be representative of the waterflood performance in Viewfield is considered for modeling. This section has been developed by use of multifractured horizontal wells completed in the Middle Bakken (main target reservoir) with a well spacing of 200 m (eight wells per section, named A through H). All eight wells started oil production within a similar time frame, and, after approximately 1 year of production, every other well was converted to a water injector.

Reservoir-Fluid Model. Conventional pressure/volume/temperature (PVT) analysis was conducted by a commercial laboratory on 12 surface-­separator oil and gas samples. Recombination of fluids at reservoir temperature (156.2°F) yields a final gas/oil ratio of 810 scf/STB. Subsequently, a series of constant-composition-expansion and differential-liberation tests was conducted on the recombined fluid to determine oil-saturation pressure, oil-formation-­volume factor, oil density, and oil and gas viscosity as a function of pressure. The Peng-Robinson equation of state and modified Pedersen viscosity correlation were tuned to replicate the PVT properties of oil and gas as a function of pressure.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 185030, “Improved Oil Recovery in Tight Oil Formations: Results of Water-Injection Operations and Gas-Injection Sensitivities in the Bakken Formation of Southeast Saskatchewan,” by S.M. Ghaderi, C.R. Clarkson, and A. Ghanizadeh, University of Calgary, and K. Barry and R. Fiorentino, Crescent Point Energy, prepared for the 2017 SPE Canada Unconventional Resources Conference, Calgary, 15–16 February. The paper has not been peer reviewed.

 

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Water-Injection Operations and Gas-Injection Sensitivities in the Bakken Formation

01 October 2017

Volume: 69 | Issue: 10

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