Field Examples Of Barrier Detection With Unsteady-State Techniques

PUBLICATION RIGHTS RESERVED This paper is to be presented at the 36th Annual Fall Meeting of the Society of Petroleum Engineers of AIME in Dallas October 8–11, 1961, and is considered the property of the Society of Petroleum Engineers. Permission to publish is hereby restricted to an abstract of not more than 300 words, with no illustrations, unless the paper is specifically released to the press by the Editor of JOURNAL OF PETROLEUM TECHNOLOGY or the Executive Secretary. Such abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in JOURNAL OF PETROLEUM TECHNOLOGY or SOCIETY OF PETROLEUM ENGINEERS JOURNAL is granted on request, providing proper credit is given that publication and the original presentation of the paper. 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 considered for publication in one of the two SPE magazines with the paper. Two field case histories involving three wells are presented, showing the effect of faulting on the pressure buildup and pressure drawdown characteristics. Example 1 has several unfavorable conditions existing - yet it shows there is a barrier present. Example 2 has two wells with drawdown curves measuring the distance to the major fault with good precision. It is concluded that barrier detection methods, using the unsteady-state techniques, are a useful exploration tool. Introduction The theory of barrier detection was published by Horner in 1951. In his paper, Horner showed how formation capacity could be obtained, what the effect of boundary conditions would have on the final static pressure, and how distances to barriers could be computed from anomalous buildup tests. Since the publication of Horner's paper, Dolan and Coauthors, and Jones have presented the results of pressure buildup and pressure drawdown tests that were near faults or other barriers. Presented here is an example which confirms the existance of a known fault and a second example which predicted the distance to a fault, which subsequent drilling proved to be correct. THE THEORY OF BARRIER DETECTION Horner developed his theory of barrier detection by the superposition of the solution of two equations. One of the equations was for the well and the other for the image well located across the barrier. The barrier is normal to the line of sight from the well to the phantom well.