A New Method for Analysis of Long-Term Pressure History

Abstract

t 1998. Smiefy of Petroleum Englnears, Inc. This -r was preperad for presenlati~et the 1998 SPE Armuel Technical tinferenca and ibitiw held In New Orfeans, Louisiana, 27-30 September 1w8. Tfds -r wss selected for presentation by en SPE Pregram Committee fOllOMng review of infomtlon mntsined "n an abstract aubrniffed by the author(s). Centents M the paper, se presented, have net bean reviewed by the Society of Petroleum Engineers and are subjscf to mrractien by the aulhor($). The materiel, es presented, does net nmssarffy reflmt any Posifim of the Society of Petroleum Engineere, IIs oMcers, or members. Papers preeented et SPE meetings ere sub~to publication review by Editorial Committees of the Swiefy of Pefroleum Engineers. Elecfrmlc reproduction, distribution, or sfcfage of any part of this paper for mmmercial purpmes Mfhout the bwiffen asent of the Society d Petroleum Engineers Is prddbitsd. Permission to repredum in print ie restricted to an ebstrect d not more than 3W web, illustrations may not h qied. The abstrati must mntain mnsPicwus edsnMedgmant et where and by Mom the papr was presented. Write Libmrian, SPE, P.O. Box 833S36, Rlchardaen, TX 750S3-3636, U.S.A, fax 01 -972-952-9W. Abstractis study presents a new way to integrate flow rate history and pressure history data in well-test analysis. The method used is an extension of the deconvolution principle to a chosen period of time before the well-test. It is based on the recovery of missing parts of the pressure history by taking into account the flow rate history and the available sections of measured pressure history. The method has the advantage of working without making any assumption about the reservoir by using the data itself to define the "model". A real example with 71 pressure poin~and 70 corresponding flow rate points shows how it is possible to recover the first 20 pressure points correctly considering that only the flow rate history and the last 51 pressure points are known.The main purpose of this procedure is to have an alternative to treat the problem of flow rate variations both before and during the well-test. In such a case, neither the deconvolution (only applicable for flow rate variations during the well-test, when flow rate and pressure are both known), nor the multirate superposition plots (too constraining on the shape of the flow rate history and on the late time reservoir behavior) can be applied properly.In addition, the principle of the method enables us to extend its use to the analysis of well-tests with pressure recording errors or missing pressure recording. Examples show that it is possible to make a good analysis of a well-test with missing pressure regions when current methods give only parts of the information.