Introduction

The Northeast Butterly Oil Creek unit is located in Garvin County, Okla., along the northern flank of the Arbuckle Mountains. Production from this field is from the Basal Oil Production from this field is from the Basal Oil Creek sand of the Simpson group, Ordovician age, at an average depth of 4,200 ft. The formation is characterized by a relatively homogeneous sand section, which is mostly unconsolidated with limey streaks through the section. The porosity is 24.3 percent with the median porosity is 24.3 percent with the median horizontal and vertical permeabilities to air 850 and 700 md, respectively. Total pay thickness is 143 ft. The natural producing mechanism is an active water drive.

The field is considered an anticlinal high, buttressing a major fault with many cross faults dividing the pool as shown in Fig. 1. Dips as high as 40 degrees exist in many parts of the field.

Encompassing only 165 acres, this field has produced 3,575,000 bbl of oil; total original produced 3,575,000 bbl of oil; total original oil in place is estimated to be 27 million bbl. It is the purpose of this paper to share some of the technology that is being used to produce this 13 degrees API gravity crude. Through the use of thermal stimulation and mechanical techniques, the recovery of this viscous, highly emulsified, sand-laden fluid has been accomplished. Reservoir and fluid characteristics are shown in Table 1.

PRIMARY PRODUCTION Because of its reserves and potential production, the Northeast Butterly Oil Creek production, the Northeast Butterly Oil Creek reservoir has attracted considerable engineering attention since its discovery. Peak production was in Aug., 1948, at a rate of 1,650 B/D. Most wells were completed for greater than 200 B/D.

A total of 13 wells were drilled from 1946 to 1948, of which one was a dry hole and one was plugged because of mechanical difficulties. As plugged because of mechanical difficulties. As wells reached high water-oil ratios, they were shut in due to being uneconomical and for lack of disposal facilities. Production declined to 3,500 bbl/month from 1957 until 1964, when thermal activities were initiated (Fig. 2).

THERMAL STIMULATION

The viscosity of the Butterly crude is approximately 2,000 cp at reservoir conditions. As can be seen on the viscosity-vs-temperature curve (Fig. 3), by raising the reservoir temperature 100 degrees F or more, the crude viscosity can be appreciably reduced. With this fact in mind, a preliminary investigation was made in 1959, followed by a feasibility study in 1962 to determine the applicability of thermal stimulation at Northeast Butterly.

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