A Study of Remedial Measures for Water-Coning By Means of a Two-Dimensional Simulator

Abstract

American Institute of Mining, Metallurgical and Petroleum Engineers, Inc. This paper was prepared for the 42nd Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Tex., Oct. 1–4, 1967. 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 PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract A computer program based on the Welge-Weber mathematical model to simulate water coding is developed. Computational characteristics such as rate of convergence, criteria for convergence, level of material balance error, sensitivity of convergence to iteration parameters, grid size and time step size are discussed. The simulator is verified by studying the effects of various factors such as vertical to horizontal permeability ratio, mobility ratio between oil and water, specific gravity differential between the two phases and flow rate on the advance of a water-cone. The cone shapes and positions are drawn for each case and the results are found to agree with known phenomena. The model is applied to the study of a stable cone height with known production rates and the results are compared with Muskat's approximate method. Muskat's prediction gives high values for stablized cone positions for reservoirs having a substantial water-oil transition zone. The simulator is applied to study the relative effectiveness of remedial measures to water-coding such as injection of oil below the perforations, production of water from the underlying aquifer through a double string and the presence of a horizontal impermeable barrier such as a cement pancake. A new method to prevent water-coning by circulation of oil as a hydraulic doublet placed at the production interval is investigated. It is found to be an effective remedial measure for water-coning problems. The oil doublet so formed is most efficient when its strength is about 20 per cent of the total fluid production. Reinjection of oil into the reservoir suppresses cone growth in agreement with the Smith-Pirson conclusions. Selective production of water and oil from their respective zones reduces the cone growth, but it gives the same overall water -oil ratio at all times and large volumes of water need to be reinjected for disposal. However, the oil doublet technique appears to be a more suitable remedial measure.