Abstract

This paper presents the results of a restimulation workover program in the Norge Marchand Unit performed during the past seven years. Upon initial completion these wells were fractured with Ottawa sand. It was suspected that a loss in fracture conductivity had occurred as a result of the proppant crushing due to the high closure proppant crushing due to the high closure pressure (7000 psi). In an effort to improve pressure (7000 psi). In an effort to improve the fracture conductivity, the wells were refractured using intermediate strength proppant. The use of pressure buildup tests proppant. The use of pressure buildup tests to select restimulation candidates improved the likelihood of having a successful treatment. The successful refractures resulted in an average increase of 50 BOPD and 98 MBO additional reserves per well.

Introduction

The Norge Marchand Unit is located within the Northwest Chickasha Field in Grady County, Oklahoma and was discovered in 1971 (see Fig. 1). The field was unitized in May 1973 and Oryx Energy was elected Unit operator. The waterflood was implemented in 1975 and fully developed by 1983. The producing formation is the Marchand producing formation is the Marchand sandstone.

Initial completions in the Norge Marchand Unit (NMU) wells consisted of perforating the entire sand at 1-2 shots per foot, breaking down with 15% HCL acid and ball sealers, then fracturing. Gel led lease crude was normally used to pump 20/40 or 10/20 mesh sand at concentrations up to three (3) pounds per gallon (see Table 1). An average pounds per gallon (see Table 1). An average stimulation consisted of 57,500 gals of gel led oil and 66,000 pounds of sand pumped down 2 7/8 inch tubing at a rate of 26 barrels per minute. None of the original fracture treatments screened out and the wells' initial potentials were in the 600 to 1200 BOPD range.

It was theorized that a loss in fracture conductivity occurred as the wells were pumped down due to an increase in the pumped down due to an increase in the closure pressure up to 7000 psi Intermediate Strength Proppant (ISP) was used to refracture wells in the Unit, in an effort to improve the wells' productivity.

GEOLOGY

Northwest Chickasha is situated in the southeast corner of the Anadarko Basin on the shelf's edge at a depth of approximately 10,500 feet (see Fig. 2). The Marchand is a shaly sandstone of the Skiatook group, Missourian series, Upper Pennsylvanian system (see Fig. 3). The productive zone is composed of a fine to very fine grained quartz with minor amounts of feldspar, interlaminated to interbedded with gray shale. Structural relief is approximately 600 feet within the Unit boundary, with dip being about 80 feet per mile to the south.

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