Incorporation Of Vertical Permeability Test Results In Vertical Miscible Flood Design And Operation

Abstract

Abstract The original analysis of the Bigoray Nisku B miscible flood indicated potential coning problems related to the level of vertical permeability. This paper presents the results of a vertical permeability lest which were incorporated into a coning study. Additional reservoir data, along with the rate information from the coning study, will be used to revise the original reservoir simulation prediction and depletion Strategy. Introduction The miscible flood in the Bigoray Nisku B pool was initiated in February 1980. It was recognized at the time that the pool was subject to coning and that controlled production rates would be required to control solvent breakthrough. Since that time, additional work and studies have been carried out to refine and optimize production strategy. History and Description The Bigoray Nisku B pool (Fig. 2), part of the West Pembina play shown in Figure I, was discovered in April 1978 with the drilling of Well 13–9. Well 8–8 was drilled about one year later, in June 1979. Soon after that time, the possibilities of a miscible flood were investigated(1) and solvent injection was started into Well 13–9 in February 1980. The same studies showed that an additional well would increase recovery and allow higher producing rates since coning prevented the wells from reaching their full potential As a result, Well 9–8 was drilled in July 1980 and Well 16–8 in October 1982. The historical production rates are shown in Figure 3. Note that prior to drilling Well 16–8 the allowable of 266 m3 /d was not being met. The full allowable is now being produced as a result of drilling this well. The Nisku B pool is a pinnacle reef with a maximum thickness of 95 m and an oil in place of 1500 × 103m3. The measured core permeability averages 130 md; however, the indicated effective permeability value is much lower. Pay is streaky and vugular. Well 13–9 is limestone, 9–8 and 8–8 have been do1omitized and 16–8 partially so. Vertical Permeability Test The original model study demonstrared that coning was going to be a potential problem and some preliminary coning studies confirmed this tendency. Prior to conducting a proper coning study, it was felt that it was necessary to compare core and in-place values of permeability and Well 9–8 was chosen for this purpose. Well Location and Test Intervals The location of the test (9-8-52-8W5M) is shown in Figure 2. The well bore configuration during the test is shown in Figure 4. Due to the relatively large thickness of the formation it was recognized that testing more than one interval would be preferable and, therefore, two tests were run over two different intervals. However, only the first test, which is discussed in this paper, was successful. In this test, oil was injected in the upper perforations, centred at 2357.0 m. and the pressure were measured at the lower perforations centred at 2374.1 m. After the conclusion of the first test, a third set of perforation (not shown in Fig. 4) were shot at 2322.9 m.