Computer Methods of Diplog Correlation

Abstract

This paper presents an automatic Diplog processing system that incorporates several new processing system that incorporates several new techniques and allows alternative processing paths. The rationale for selecting the product-moment method as the primary correlation technique is given, and the algorithm for variable window-length correlation and infinite-clip methods discussed. In the screening section, several approaches to grading and screening of picks to improve the appearance of the machine-correlated Diplogs are discussed. The derivation of flexible vector analysis equations for dip calculation is also presented. presented Introduction Modern logging technology appears to be on a definite trend toward the recording of well log data on magnetic tape. The use of digital tape for Diplog data processing has been increasing for several years and will continue to become more significant. The use of magnetic tape for processing theoretically makes the turn-around time faster and makes screening and filtering of large amounts of data feasible. Processing of digital tapes can take any of several routes, some better than others for a particular set of conditions. In this paper, we particular set of conditions. In this paper, we present several of the possible approaches to present several of the possible approaches to processing the data and explain the rationale for processing the data and explain the rationale for choosing a particular one. In addition, several approaches that we feel are both new and useful are presented. RECORDING SYSTEM The system of digital recording that we now use is composed of the following pieces of equipment:tape deck,tape controller,encoder andpanel for service being recorded. The first two of these are built into a digital taping unit for easy use in the field. This tape control panel and the taping unit in conjunction with the normal logging panel for the particular service being recorded are panel for the particular service being recorded are necessary for digital taping. All analog signals from the instrument are first routed to the service panel. This panel functions as a demodulator for modulated signals, a signal separator for signals on the same line, an encoder for pulse data, and as a filter for noise control. The output from the Diplog service panel in the form of 10 separate analog lines then goes to the tape control unit. The control unit is essentially an amplifier unit providing the recorder with signals in its acceptable range of 0 to 10 v. The signals are calibrated from this panel during the setup procedure. In addition to amplification of signals, procedure. In addition to amplification of signals, the tape controller receives signals from the depth encoder (remote from the rack) and converts them to the proper control pulses for the recorder. The encoder generates either 128 or 256 pulses/ft. These are divided by 2 or 4, respectively, to give the 64/ft necessary to drive the tape recorder synchronously with tool movement. One type of digital field recorder is an SIE series 3312 recorder. Up to 10 channels of data are encoded onto tape by this recorder. The channels are divided into two groups designated as "fast" channels and one "slow" channels. During each partial sequence, each of the five "fast" channels partial sequence, each of the five "fast" channels and one "slow" channel are sampled. After eight partial sequences have been completed (one full partial sequences have been completed (one full sequence), each of the slow channels mill have been sampled and recorded. This dual sample rate allows the recorder to sample the fast channels more than twice as often as would be possible using a single-rate system. Only signals that change relatively slowly are recorded on slow channels; thus no degradation of the data is noticed. Each channel is recorded as two adjacent frames, the most significant six bits in Frame 2. These frames are written incrementally on standard 7-track tape. Since stopping the multiplexor would cause a loss of data, field capes are recorded as continuous records. Generally, about 1,500 ft of Diplog data is recorded per tape. Since the tapes are recorded without gaps and this amount of log represents more than 1 million bytes of data, even most large computers cannot handle the tapes directly. SPEJ P. 31

Computer Techniques for the Zoning and Correlation of Well‐logs*

“…Examples of the fixed interval method, discussed earlier as cross correlation in the space and frequency domains, include early papers by Moran, Coufleau, Miller and Timmons (1962), who were among the first to describe the use of a digital computer in the analysis of digitally recorded well-log data, and more recently Schoonover and Holt (1973) and Schoonover (1974). Kemp (1980Kemp ( , 1982 used the idea of planarity to constrain the identified correlations.…”

Formation Dip Determination Using Digital Wellsite Processing Techniques

“…Both programs consider a correlation acceptable only if the peak coefficient is sufficiently greater than the average value of coefficients in the correlogram. An estimate of the convexity of the correlogram is also used by both programs to screen out poor correlations (3). Each program performs a qualititaive check of curve activity, or variation, and similarity of activity among all the pad curves.…”