A Comparative Study of the Characteristics and Susceptibility of Pattern-Type Water-Injection Well Networks From the Viewpoint of Balanced Waterfloods

Abstract

Tong, Xian-zhang; Scientific Research Inst. of Petroleum Exploration and Development Abstract In this paper, some standard geometrical flood patterns of "n-spot" are compared with each other on the basis of their respective susceptibility to the balance between total fluid injection and withdrawal rates by use of a basic parameter, Fm, the ratio between the average PI of production wells and the injectivity index of injection wells. The characteristic parameter. Fm, of a reservoir basically is dominated by the reservoir rock and fluid property as well as by completion practices. property as well as by completion practices. Each pattern of well networks deserves preference under certain specific circumstances. All factors other than F, being equal, the five-spot network offers greater total liquid deliverability when Fm lies within the range 1 to 1. 5. When Fm, is smaller than 0. 5, the inverted nine-spot network begins to show its superiority. Formulas and graphs showing relationships between n and Fm are presented for comparison and selection of optimal patterns for different circumstances. Introduction The experiences accumulated from the oil industry throughout the world during the past 50 years have proved that, under appropriate geological, technical, and proved that, under appropriate geological, technical, and economic conditions, an oil reservoir development program utilizing natural or artificial water-drive program utilizing natural or artificial water-drive mechanism often exhibits distinct superiority over the others. On the premise of achieving the highest attainable ultimate recovery, at the same time maintaining a reasonably high and stable rate of oil production during the main phase of producing life, reservoir engineers usually consider various kinds of water-injection projects in planning a development program. Since the early 1950's, many giant oil fields with reservoir rocks more or less heterogeneous in nature have been discovered and developed in different countries; among them are the well-known Pembina oil field in Canada and the Daqing oil field in China. The history of development of these fields proved that, for the sake of maintaining a reasonably high liquid withdrawal rate over a sufficiently long period, and at the same time attaining a high water-drive efficiency, various kinds of pattern-type well networks had to be adopted in planning pattern-type well networks had to be adopted in planning a development program. In the U. S., where the regular and irregular pattern-type well networks for secondary recovery are commonly practiced, the five-spot pattern is most popular. Although the interlaced pattern-type injection and production well networks have been used in oil production for many years, not much treatment has been production for many years, not much treatment has been undertaken from both theoretical and experimental aspects to summarize some niles about the respective merits of the different networks. Muskat, in his classic work, Physical Principles of Oil Production, presented the most comprehensive review of the theory relevant to the steady state flow capacity of the various pattern-type well networks. He also presented steady-state equations for computing water breakthrough time and sweep efficiency for different networks. Craig has given rather comprehensive comments about the waterflood pattern. SPEJ p. 892