Successful Stimulation Techniques in a Low Permeability Shallow Sandstone Reservoir
Authors: O&apos;Neil D.E. , Broschat R.E. 
Published: December 2007

This paper was prepared for the Rocky Mountain Regional Meeting of the Society of Petroleum Engineers of AIME, to be held in Casper, Wyoming, May 15–16, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made.
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Abstract
The Spearfish oil reservoir in the Newburg field of north central North Dakota is a shallow, silty sandstone with low permeability and porosity. In the past, conventional fracture porosity. In the past, conventional fracture treatments in this reservoir were unsuccessful due to the presence of a prolific water sand about 25 ft above the oil pay zone. At the rates and pressures required using conventional fracturing fluids, communication with the overlying water sand usually resulted when these wells were treated.
Recently, many of the producing wells in this field have been successfully stimulated using ultraviscosity fracturing fluids. These fluids permit lower treating pressures and pump rates without premature sand out. Matrix acidizing techniques have also been successful in treating low capacity wells and wells that previously had communicated with the water sand. previously had communicated with the water sand. In cases where water breakthrough did occur, an excellent method of source detection and water shut-off has been found. A differential temperature survey has been used to locate the source of water entry and a squeeze treatment consisting of a long chain polymer fluid followed by low water loss cement has been successful in obtaining water shut-off.
Results of these stimulation treatments to date show that a low-permeability sandstone in close proximity to water can be successfully stimulated using the latest industry technology.

Introduction
The Newburg field is located in north central North Dakota approximately 60 miles northeast of the city of Minot (Fig. 1). Oil production in the Newburg field is from two production in the Newburg field is from two formations, the Spearfish sandstone and the underlying Charles limestone.
The Spearfish pay sand lies on a fractured erosional unconformity directly above the Charles limestone. In Fig. 2 a type log of the Newburg field is shown together with descriptions of the lithology of these zones. Fig. 2 also shows the location of the Spearfish water sand, which has created many problems in attempts to stimulate the Spearfish pay zone.
Spearfish oil production is from two basal sands, locally denoted as P-1 and P-2. The P-1 is the main pay sand being evenly distributed throughout the field. In several parts of the field, the P-2 is tight or absent. The Spearfish oil accumulation is stratigraphically controlled with the reservoir becoming tight and impermeable on the updip east side of the field.