API RP 31A:1997 (R2012)

The variety, use, and value of log recordings of subsurface properties have been greatly increased and expanded since the last revision of Recommended Practice 3 1. A wide diversity of log measurements (from both open and cased hole) are routinely being combined to interpret the original status of newly drilled wells and to evaluate performance and potential throughout each well's life. Standardization of the log form and data presentation will allow the user to conveniently combine log data from various devices and dates. Recognizing the wide variability in the tools covered by these recosnmendations, this document attempts to preserve flexibility wherever possible. The format selected allows for presentation of data that can be measured as a series of values at specified well depths. Consequently, this document can be easily applied to most logging measurements, and will serve as a reference document to technology-specific documents. This document makes no recommendations concerning the standard log record (refer to Section 4) for measurements that are data series at individual depths (for example, pressure transients, video images, sonic traces, and so forth). To the extent that recommended practices for the presentation of such data are appropriate, they should be included within separate Recommended Practices for the technologies involved. In addition to the recommendations concerning the format for presentation of log data, this document provides several enhancements to the standard log heading. These changes are designed to provide the user with a more complete set of information in consistent locations on all logs. Due to the increasing use of tool calibration and data processing while logging, recommendations are provided concerning documentation of equipment history and processing software. One should identify tool-specific information in other appropriate recommended publications. The recommended additions to the content of the support information included with hardcopy presentations of well log data, as described in the following, should also be included with digital recordings of the same well logs. The recommended digital formats to be used are provided in API Recommended Practice 66. The recommendations contained within API Recommended Practice 31A provide some flexibility regarding the dimensions of the actual print field used in the hardcopy presentation of well log data. This flexibility will accommodate the use of commonly available printers and paper sizes as optional alternatives to the 6.25-inch by 9.25-inch fanfold paper on which log data has been traditionally printed. Example figures conforming to this document and printed at the dimensions required for 8.5-inch by ll-inch paper are provided. The changes made to accommodate this flexibility in paper and printer selection will in no way alter the actual scaling of the log data. Log data curves will precisely 'overlay,' regardless of the choice of paper or print field dimensions. Any hardcopy presentation of log data that meets all of the information content and format specifications described in the text of this document shall be considered to be in conformance with it.