01-Input Data Errors

01-Input Data Errors - Effects of Errors in Input Data 1...

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Effects of Errors in Input Data 1 SPE 39773 - Errors in Input Data and the Effect on Well-Test Interpretation Results Many, if not most, of the observations offered in this paper are part of the working knowledge of the full-time well test analyst. However, these observations have not been systematically catalogued and discussed in the literature. The purpose of this paper is to provide just such a systematic catalog and discussion.
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Effects of Errors in Input Data 2 By way of introduction, we will pose two problems which for the well test analyst. In “Sources of Error in Input Data,” we will look at where the input data for well test interpretation come from, and the likely magnitude of error for each input variable. In “Effectsof Error on Results of Well-Test Interpretation,” we will consider the effects of errors in each of the input data on the results obtained from a well test interpretation. In “Examples”, we will provide the solution to the problems posed in the introduction. Finally, we will conclude the presentation with a brief summary.
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Effects of Errors in Input Data 3 Well “A” has the following estimates from a pressure buildup test: Permeability of 10 md, Skin factor of 0, Distance to the nearest boundary of 250 feet. These estimates were obtained by using the perforated interval for the net pay in the interpretation of the buildup test. If a detailed log interpretation shows that the actual net pay is closer to 50 feet, how will this affect our estimates? We know that kh should not be affected, so we can estimate the true permeability to be 5 md. But how are skin factor and distance to the boundary affected?
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Effects of Errors in Input Data 4 Seismic interpretation indicates there is a boundary 300 feet from Well “B”. PBU test interpretation indicates that the nearest boundary is 900 feet away. Can these two interpretations possibly be consistent? If so, what can cause this much error in the distance estimate? This paper will allow the engineer to quickly answer these questions.
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Effects of Errors in Input Data 5 For the purposes of this presentation, the data used in well test interpretation may be divided into three categories: Data from interpretation of open hole logs; Fluid property data; and Other input data.
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6 Analysis of open-hole logs provides estimates of porosity, water saturation, and net pay thickness for use in well test interpretation. None of these properties are measured directly by open-hole logs. Instead, physical properties such as hydrogen index, sonic travel time, electron density, and natural radioactivity are measured. The desired properties, porosity, shale content, water saturation, and net pay thickness, are inferred from these measurements. Errors can creep into log-derived estimates in at least 4 different ways.
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This note was uploaded on 04/05/2011 for the course PETE 689 taught by Professor Staff during the Spring '08 term at Texas A&M.

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01-Input Data Errors - Effects of Errors in Input Data 1...

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