NZ197637A - Recording seismic array positions by digital data processing - Google Patents

Description

197637 Priority Date(s): 16." Complete Specification Filed: Class: ^5.Q•I »..•••••••••••••*•• ;Publication Date: . ^ ^ ^86 ;P.O. Journal No: ;\ ;NEW ZEALAND ;PATENTS ACT, 1953 ;No.: Date: ;COMPLETE SPECIFICATION ;IMCflMCr ;METHOD FOR AUTOMATICALLY -HIDICACATIN6- AND RECORDING ;PARAMETERS THAT SPATIALLY DEFINE LOCATIONS OF SEISMIC EXPLORATION SPREAD AND SOURCE ARRAYS X/We, CHEVRON RESEARCH COMPANY, a corporation duly organized under the laws of the State of Delaware, United States of America, of 100 West Tenth Street, Wilmington, Delaware, U.S.A. and having a place of business at 525 Market Street, San Francisco, California, United States of America hereby declare the invention for which % / we pray that a patent may. ;be granted jto une/us, and the method by which it is to be performet to be particularly described in and by the following statement: - i 27 MAR 1986' ;. . i . ;(followed by page la) ;0 1 ;05 ;10 ;15 ;20 ;25 ;30 ;35 ;40 ;- let ;197637 ;METHOD FOR AUTOMATICALLY INDICATING AND RECORDING PARAMETERS THAT SPATIALLY DEFINE LOCATIONS Or SEISMIC EXPLORATION SPREAD AND SOURCE ARRAYS ;SCOPE OF THE INVENTION ;This invention relates to seismic exploration and more particularly to methods for insuring integrity of field shooting and recording operations during exploration for hydrocarbons and the like. ;In one aspect, the present invention provides for dynamic control of the field shooting and recording operations so that the latter actually correspond to the advanced specifications for those operations; as a result, recording operations can be coordinated with the specified shooting (or vibrating) operations. In accordance with another aspect, the present invention provides for the generation and recording of data including array and source geometry information on a recording media as header data in addition to the recording of seismic data representing acoustic signals received as the consequence of shooting (or vibrating) operations. ;BACKGROUND OF THE INVENTION ;In seismic exploration, proposed prescriptions for shooting (or vibrating) and recording operations must be followed — precisely — in the field, particularly in field techniques involving so-called Common Depth Point Recording (or CDPR) operations in which changing sets of sensors were used in association with successive shots to provide multiple stacked recordings. (In all of the following teachings, the words "shots" and "shooting" will be used for the part of the operation in which the sound waves are generated and sent down into the sub-surface. It will be appreciated, however, by those skilled in the art, that the same teachings apply where the sound waves are generated by large vibrators at the surface rather than by explosive shots.) ;In the CDPR process, sensors and energy sources are positioned at a first series of spatially (geometrically) related locations, to produce a first record. Subsequent records are then made with the sensors and the energy source occupying new locations. However, the sensors and energy source normally maintain the same relative spatial relationship to each other during the field operations . ;Advancement of the sensor locations (in CDPR operations) employ a technique commonly known as "roll-along" . Relative advancement of the sensor array is commonly done in a very rapid manner using a switching device called a rollalong switch (such as shown, e.g., in my U.S. Patent 3,618,000, November 2, 1971 for "Rollalong Switch"), in which a large number of sensors can be con-trollably provided at any programmed interval along the recording line. Through the use of multiple pair cables extending along the line, these sensors are connected into the input receptables of the rollalong switch. The design of the switch permits a certain number of the sensors, called the "active" array, to be interconnected to the input of the geophysical seismic recorder and keeps track of the position of one end of the active array relative to the number of recording channels available (say, any position within l-in-60 channels). Not only can the switch select any contiguous group of sensors, from the total number positioned along the line, as the "active" array or spread, but it can also add gaps in the active spread using one or more "inactive" groups as the gapping members, a technique usually used when a large energy source is positioned at the center of the active array. (A "gapped" array for a 24-sensor record, for example, consists of sensors 1 through 12 and 15 through 26 with sensors 13 and 14 left disconnected by the rollalong switch. ) ;Computer processing of the CDPR field data (now commonly done by large centralized computer facilities) requires not only accurate time-versus-amplitude seismic ;01 ;05 ;10 ;15 ;20 ;25 ;30 ;35 ;40 ;-3- ;reflection data but also requires "housekeeping" data describing associated source and sensor geometry as the former was collected. These latter data consist of, inter alia, positional locations for every sensor in each "active" array during the recording sequence, the location of the energy source, and the location and size of the gap (if any). To provide the above, the usual field procedure is to determine the ground locations by survey prior to the recording operations. The location and direction of the line is referenced to know geographic locations or geodetic survey points. The location of each sensor (or sensor group) and energy source is surveyed in and marked with a survey stake having an identification number representing a ground location. These locations are written down in the survey log for that particular seismic line. The surveyor's log thus contains part of the geometrical data that must be added to the seismic data after the latter has been recorded and is ready for processing. ;Another requirement of the geometrical data is developed during the recording.process. It relates to data entered into the "observer's log". (The operator of the seismic recording system is commonly called the "observer".) The observer's log contains, for each record sequence, the spatial extent of the active sensors usually identified by ground locations of the sensors at each end of the active array. In the event that the active array contains a gap, the location of the gap will be specified relative to adjacent active sensor locations. The observer's log also contains the location of the energy source for each record. In some cases, when a presurveyed line is recorded, the energy source cannot be located at the location designated for it during the survey. In these situations, the shot location from the observer's log must be used in processing instead of the original survey data. The observer's log also contains information that infers or describes spatial irregularities in the active array imposed by field conditions when the line is recorded . ;- 4 - ;197637 ;As previously Indicated, the rollalong switch tracks the position of active array (for Identifying the location of the "active" sensor array Including gap). While some rollalong switch units provide for transferring such array data directly to the field recorder (recognizable as header data on the digital seismic tape), these data are not In terms of true ground location, but In an arbitrary numbering sequence, relative to a particular reocrdlng vehicle location. The true ground location of the recording vehicle must therefore be entered Into the observer's log in order to convert rollalong switch positions to true ground locations. ;The foregoing description of geophysical seismic data recording operations Indicates conclusively that the recording of seismic reflection data must be supported by accurate and sufficient correlative data so as to accurately define spatial source and sensor geometry relative to a permanent geographical location. It also Indicates that separate types of cross-checking materials, for documentation, are needed as the data Is collected, including the steps of generating, formatting and displaying spread and sound geometries for both present and next-In-time shooting and recording sequences. ;Accordingly the Invention consists In a method of calculation, ;storing and recording positional data associated with a digital exploration system during generation and collection of seismic data by a source-detector array positioned at known locations along a I Ine of survey, said positional data being generated as bits of digital data stored In a microcomputer system Including a mlcroporcessor unit (MPU), ;memory units, and a series of display/storage and switching devices Interconnected to each other and to a digital field system (DFS) via a system bus, whereby errors in exploration activities are reduced, and annotation of exploration activities Is automatically added, comprising: ;(a) establishing In digital format via said microcomputer system, array geometry and exploration parameters that allow annotation In sequence of exploration activities along said line, ;(b) automatically displaying at said display/storage and switching devices of said system, at I east a portion of data of (a) in alpha-numeric form for operator examination and correction, if required, and ;(c) automatically recording said portion of data of (a) as header data so as to provide full annotation of exploration activities whereby errors In such exploration activities can be discovered and accounted for. ;Ground position controllers for automatically indicating and recording parameters that spatially define locations of seismic exploration spread and source arrays are described and claimed In New Zealand Patent Specification ;Figures 1 and 2 Illustrate an exploration system incorporatlng the present Invention in which an energy source and an array of sensor (connected to a recording truck) are Illustrated. ;Figures 3 and 6 are block diagrams of the ground positioned controller of the present Invention used within the exploration system of Figures 1 and 2. ;Figure 4 is an Isometric view of a display panel of the controller ;Figures 3 and 6. ;01 ;-6- ;FIG. 5 is a block diagram of a microprocessor unit of the controller of FIGS. 3 and 6. 05 FIG. 7 is an imaginary rendition of header data encoded onto magnetic tape using the controller of the present invention in association with the recording unit of the exploration system of FIGS. 1 and 2. ;FIG. 8 is a block diagram of portions of the 10 circuitry comprising the controller of FIGS. 3 and 6, and recorder unit used in the exploration system of FIGS. 1 and 2. ;FIGS. 9A-9C are flow diagrams which illustrate the method of the present invention. ;15 FIG. 10 is a partially schematic diagram of the recorder unit of FIG. 8 illustrating a sequence of operations, associated therewith. ;DESCRIPTION OF ;PREFERRED EMBODIMENTS OF THE INVENTION ;2q FIG. 1 illustrates operation of seismic explora tion system 9 of the present invention. ;As shown, system 9 includes digital field system (DFS) 10, housed within recording truck 11 and electrically interconnected via a multiwire geophysical cable 12 25 to an array of sensors 13 positioned at the earth's surface 14. ;Ground locations 15 are represented as surrounding both the array of sensors 13 and seismic energy source 16, all positioned along the surface 14. As pre--jq viously mentioned in the CDPR collection process, the ground locations 15 would, more likely than not, have been previously surveyed prior to implementation of the seismic surveying operation along the line of survey 17 in the direction of arrow 18. Hence, each of the locations 15 can be designated by a particular position number (or P number) along the line 17. The P numbers set forth in FIG. 1 include the numbers 300, 301... 329. Also, the number of sensors 13 forming each array (as the data is ;40 ;01 ;-7- ;collected) is identified by the sequence numbers N, N+l... N+M designating the length of the active array as the 05 sensors 13 are advanced in the direction of arrow 18. ;Annotating the positions of the sensor arrays is aided by the fact that each sensor is associated with a particular data channel 1, 2...K of the DFS 10 as the data is collected. For usual operations K can be 24, 48, 60, 10 96, 120, etc., as required, although, of course, the present invention is not limited to a particular channel capacity number, but can be varied to accommodate any field arrangement. Each sensor position and each source location can be indicated using the ground position con-15 troller 20 of the present invention in conjunction with recording unit 21 of the DFS 10. ;FIG. 2 illustrates ground position controller 20 in more detail. ;Briefly, the ground position recorder 20 20 operates in the field to insure integrity between prescribed and actual field shooting and recording operations by a series of steps, namely, storing, manipulating and displaying data related ;(i) to field positions of the source and sensor 25 array by position number, ;(ii) to array and source geometrical locations (both present and next-in-time) based on field geometrical algorithms and ;(iii) to recording array and source parameters 30 so that realistic annotation of the subsequently collected seismic data, can be made. For these purposes, the operator utilizes encoded data provided initially by him using encoders 26, manipulated results generated by the controller 20 based on part in stored relationships within 35 the microcomputer 25, and finally indicating geometrical data set forth at displays 27 and as header information at recording unit 21. ;Since the present invention deals conveniently with the CDPR process, the array of sensors 13 and source 40 of energy 16 are continually "rolled forward" in the ;01 ;-8- ;direction of arrow 18 using rollalong switch 22. That is to say, after the seismic data has been recorded at the 05 digital tape recording unit 21 (after amplification by amplifier 24), the array of sensors 13 (and source 16) located at a first series of positions P as shown, are "rolled forward" in the direction of arrow 18. Note that the changing of the active array pattern of FIG. 1 in the 10 aforementioned manner is identified by the array sequence designated N, N+l... N+M, as previously mentioned. But, the array and source geometry is always known at the recording truck 11 provided the positional locations 300, 301, 302...P of FIG. 1 for the particular active array N, 15 N+l... N+M are correctly identified and recorded during each recording cycle, via operation of the ground position controller 20 of the present invention; of particular importance is the manipulation of data associated with the field geometry of the sensors 13 and source 16 via geo-20 metrical and performance algorithms stored within microcomputer 25 of the controller 20. ;As previously mentioned, microcomputer 25 is used to predict correct array positions as the rollalong switch 23 switches between "active" and "inactive" arrays 25 of sensors. The microcomputer 25 can also interact with the rollalong switch 22, provided the latter is capable of accepting the multi-bit codes conventionally generated by the microcomputer 25. (In this regard, an approved roll-along switch is manufactured under the tradename "Rola-30 long Switch", by Input-Output, Inc., Houston, Texas, and consists of a series of contacts attached to a central shaft of a stepping motor controlled via a digital input code from the microcomputer 25.) ;Rollalong switch 22 usually includes a display 35 (not shown) associated with one or two of the locational positions of the active array of sensors 13. Such display, of course, changes as the active array changes sequential pattern in the manner of N, N+2... N+M, as shown in FIG. 1. The rollalong switch 22 also includes a 40 digital generator (not shown) for generating a second ;01 -9- ;multi-bit code indicative of the position P of a member of the sensor array as header indicia at the recorder 21. 05 However, as previously mentioned, the latter digital code represents only an arbitrary number and is not a true geodytic location. ;FIG. 3 illustrates microcomputer 25 of controller 20 in still more detail. ;10 As shown, the microcomputer 25 includes a system bus 28 used to connect encoders 26 and displays 27 via I/O interfacing array 34 to microprocessor unit 30 (MPU) of /the microcomputer 25. Also connected via the bus 28 and ports 29 are interrupt controller 31, RAM 32, ROM 33 (in 15 addition to I/O interfacing array 34) which operates in conventional fashion to calculate, manipulate, store and display position data associated with the exploration operation. Note that the I/O array 34 not only links the MPU 30 with the encoders 26 and displays 27, but it is 20 also used to provide data to the printer 35 under control of MPU 30 to generate a permanent record of the displayed data at displays 27, if desired. ;Bus 28 essentially comprises three separate buses, a data bus, an address bus and a control bus. The 25 data bus is conventional: it not only carries information to and from MPU 30, but it is also used to fetch instructions that have been stored in ROM 33, as required, as well as carries data from/to the encoders 26 and displays 27 of FIG. 2, by way of (or independent of) RAM 32. 30 Addressing segments of the data is the annota tions function of the address bus. It is capable of selecting a location in RAM 32 or ROM 33 or a particular address in the MPU 30 when appropriately signaled, say by interrupt controller 31. The control bus controls the 35 sequencing and nature of the operation using common selector commands, e.g., "Read", "Write", etc. ;Additionally, it should be noted, the system interrupts are usually carried via the control bus to implement the scheduling and servicing of different ports, 40 as required by operations. In the present invention, ;-10- ;interrupt controller 31 handles seven (7) vectored priority interrupts for the MPU 30, as explained below, including an end-of-record interrupt (EOR) generated by the digital field system 10, FIG. 1, to indicate the end of the collection cycle, and to initiate operations in the next-in-time cycle. ;In general, in servicing the interrupts, preservation of program status is required and is easily carried by the MPU 30. Since the controller 31 is both vectored and priority oriented, it has the responsibility of providing vectored interrupts to the MPU 30, of identifying the nature of the interrupt, (or its branching address) and of establishing priority between competing interrupts. ;In particular in servicing the EOR interrupt, the steps set forth in FIGS. 9B and 9D are executed to bring about automatic updating of the array and source geometry to achieve the next-in-time collection of data, based in part on the field algorithms contained in equation sets I, II, III or IV set. forth below. ;FIG. 4 illustrates the nature of the data provided at encoders 26 and displays 27. ;The operator initially calibrates positions of the exploration array and source with previously surveyed geographical stations. Information has been already encoded via the encoders 26 for use by microcomputer 25 before operations begin. Encoded data at encoders 26 includes: ;(i) truck location (vis-a-vis survey stations of known geographic location) encoded at encoder sub-element 40; ;(ii) slave truck location (if applicable) ;encoded using encoder sub-element 41; ;(iii) reference station location (where the end of the spread is initially positioned) encoded via encoding sub-element 42; ;(iv) initial location of the energy source encoded using encoder sub-element 43; ;-11- ;(v) the number of shots or sweeps encoded at sub-element 44; ;(vi) the initial gap position, stored at sub-element 45; ;(vii) the gap spacing encoded using encoder sub-element 46; and ;(viii) gap roll increment encoded using sub-element 47 . ;The operator also has the initial responsibility of encoding other data which, for the most part, does not change during the survey. In this regard, the operator may have to only initially encode shot depth and size (at sub-elements 48 and 49), shot direction and offset (at sub-elements 50 and 51) as well as data related to the spread, as to its direction (at sub-element 52) and the distance between groups (at sub-element 53) . ;Switch arrays generally indicated at 54 and 55 are also set by the operator. Data provided by these switch arrays, relate to two or three possible switch states of the switches 56-66 which are, for example, related to the type of survey and run conditions occurring after the survey is underway. ;[In this regard, the functions of the switches are as follows: Switch 56 specifies line direction; ;switch 57 specifies truck rank, i.e. determines if the reference truck is the master (or slave) in relationship with an alternate truck; switch 58 specifies operations in either a serial or in a parallel mode, the mode being related to whether one or two arrays of geophones are used in-line or parallel to the corresponding source line; pushbutton switches 59 and 60 relate to start up and to alarm reset functions respectively; switch 59, of course, initializes operations after all synchronization has been completed; switch 60 turns off the audio alarm in the event that a signal of some importance has been generated causing the alarm to also activate; transmit switch 61 "triggers" the energy source, and is operative only after the operator is assured the correctness of the array and ;01 ;05 ;10 ;15 ;20 ;25 ;30 ;35 ;40 ;-12- ;source positions as displayed at displays 27; switches 62 and 63 related to (i) the "trigger" link associated with the activation of the source (electrical wire-line or radio) and (ii) whether or not the roll switch 22 (FIG 2) is to be in an active or passive state. Three-position switch 64 establishes whether or not the operation is to be in a manual, automatic or test mode; update switch 65 operates only when the switch 64 is in the manual mode and is used (in manual mode) to initiate advances of the roll switch so as to generate new ground locations for the array after the recording cycle has been completed; and switch 66 is a conventional power-on switch.] ;Displays 27 may be conventional LED segmented displays except that they are microcomputer implemented. Primary purposes of the displays 27: to provide data to the operator so that determinations as to whether or not the system is functioning correctly can be made, and to allow the operator to act as an independent cross-checker of the correctness of the displayed ground locations. The data at displays 27 relate for the most part to the type of run being undertaken and survey conditions. ;[In this regard, the nature of the displays 27 is as follows: subdisplays 70 and 71 indicate shot location and number of shots per location, respectively; sub-displays 72-75 relate to geographic locations of the active array as a function of time; subdisplay 76 specifies the position of the slave reference; status subdisplay 77 specifies (by code) the occurrence of certain activities during the exploration operation which may be accompanied by an audio alarm to indicate the immediate need for operator intervention, the meaning of the status code at subdisplay 77 being as set forth below, in Table I. ;-13- ;TABLE I ;Code Activity ;0 Setup for sequence start operation ;1 Geometrical mistie ;2 Ready for update or update in progress (if in auto mode) ;3 Roll Switch Moving ;4 Roll Switch (Stopped in position) ;5 Roll Switch Disabled ;6 Slave Reference Code Received ;7 Transmission Reference Error (slave reference code not received) ;8 Load Ref Output At Shift Register ;9 Transmit (one bit of ref code) A Gap Set Mistie ;D Occurrence of Last Shot ;IX Beeper On With Status Displayed as to Code ;0, 1, ... 9, A, D, alone. ;53 Step Roll Switch Up With Beep on and Code " ;93 Step Roll Switch .Down With Beep on and ;Code "3". ;Explanation of Table I: status code'"0" occurs any time that the controller 20 is powered up to cue the operator that all input data at the encoders 26 must then be set. Sequencing start button 59 terminates the cueing operation; status code "D" indicates that the last shot position is at hand and thus, the truck location and connection station vis-a-vis the array must be changed; status codes "3", "4", "5" and "53" and "93" indicate certain roll switch activities. If there are errors in the programmed exploration activity, warning codes are also generated by the status codes "1"; and "7".] ;OPERATIONAL SEQUENCE Assume the operator has initially calibrated th start-up positions of the array and source with the surveyed locations. As previously indicated in regard to FIG. 4, this entails encoding of positional data via ;-14- ;encoders 26 in conjunction with proper setting of the switching arrays 54, 55. The result: corresponding shot, spread and associated data appear at the displays 27 due to the interaction of data relationship established ■ through operation of the microcomputer 25 of FIG. 2. In order to better understand how the present invention uses all data, perhaps a brief overview of the hardware aspects of the microprocessor 30 is in order and is presented below in connection with FIG. 5. ;It should be initially noted that MPU 30 is preferably an Intel 8085 microprocessor, a product of Intel Incorp., Cupertino, California. As is well known, it has a microprocessor and controller integrated into a single chip. It also includes an array of registers 82 tied to an ALU 83 via an internal data bus 84 controlled via control unit 85. Program counter 86 and instructional register 87 have dedicated uses; the other registers, such as accumulator 88, have more general uses. In the 808 5, expanded control functions result because the low-eight (8) address bits have the capability of being multiplexed. Such operation occurs at the beginning of each instructional cycle; the low-eight address lines appear via ALE line 89 for control of different elements of the location, including encoders 26, displays 27, and printer 35 through I/O interface array 34 of FIG. 6. ;As shown in FIG. 6, while the I/O array 34 is conventional, it must be capable of handling a series of 8-bit independently addressable codes. For this purpose, it preferably comprises a multiplicity of 8-bit I/O port chips indepedently addressable via ALE line 89 of FIG. 5 of the MPU 30. Each 8-bit I/O port chip preferably comprises an 8-bit latch combined with a 3-state output buffer in which each can be separately driven. In determining location of data via address decoder 38, the MPU 30 also must manipulate the data using known geometrical relationships in which encoded positional data can be translated as required, depending on several factors. ;-15- ;Assume the survey has just been started; the operator has encoded all pertinent data via the encoders 26. Also switch arrays 54, 55 have been properly set. Initially the control and reference location position data from encoders 26 (and the switch arrays) are fetched by the MPU 30. The MPU 30 next performs the required manipulation of that data to define spatial array and source geometries of interest in the manner of FIGS. 9A and 9C. Such manipulation of data includes execution of the steps associated with the basic power-up routine of FIG. 9A and the sequence start routine of FIG. 9B, including accessing the calculated data to displays 27 for operator perusal. ;DATA ARRANGEMENTS AT DISPLAYS 27 Values of data appearing at displays 27 of FIG. 4 are, of course, dependent upon use of certain geometrical equation sets, viz. equation sets I, II, III and IV set forth below, stored in the MPU 30 and selectively utilized by the controller 20 as required. ;SEQUENCE START EQUATION SET I Assume both the ground location numbers and data channel numbers increasing along the seismic line in the direction of arrow 18; accordingly, the following set of equations control operations: ;(1) RLSP = REF-NP-TR ;(2) END 1 = REF ;(3) END 2 = REF+GPNO+K-1 If GPNO = 0 ;(4) GAP 1=0 ;(5) GAP 2=0 If GPNO > 0 ;(4) GAP 1 = REF+GPLOC-1 ;(5) GAP 2 = REF+GPLOC+GPNO ;(6) ROOM = TR-REF-GPNO+1 ;01 ;-16- ;05 ;10 ;15 ;20 ;25 ;30 ;35 ;Table II, below, defines the notations used above in connection with the Equation Set I: ;Notation ;SHLO ;SHNO ;REF ;ROOM ;TR PNO GPLOC K ;END 1 ;END 2 GAP 1 ;GAP 2 ;RLSP ;NP ;GL( + ) ;TABLE II ;DEFINITION Energy source location Energy source number Location of reference sensor ;No. of rollalong switch positions available for advancing the active spread Ground reference for recorder location Number of geophone groups in the GAP Location of the GAP ;Number of data channels in recording system ;(24, 48, 60, 96, 120, etc). ;Ground location of the geophone group interconnected through the rollalong switch to the first data channel of the recorder. Ground location of the Kth data channel Ground location of the data channel below the GAP on the first data channel side. Ground location of the data channel above the GAP toward the Kth channel. ;Rollalong switch position required for a desired active spread location. ;Number of rollalong switch positions available minus 1. (N-l). Rollalong switch must be configured for K+N inputs and K outputs. ;Ground location numbers along the seismic line increasing numerically in the direction in which the active geophone array is advanced for each successive record sequence ;40 ;«••••••• ;••••••* • • 01 -17- Notation DEFINITION- 05 GL(-) Ground locations numbers decreasing numeric ally in the direction in which the active spread is advanced.

CH(+) Seismic data channel increasing (1 to K) numerically along the active spread in the direction in which the active spread is advanced.

CH(-) Seismic data channels numerically decreasing (from K to 1) in the direction in which the active spread is advanced.

GAP 2 Ground location of the data channel above the GAP toward the Kth channel.

RLSP Rollalong switch position required for a desired active spread location.

NP Number of rollalong switch positions avail able minus 1. (N-l). Rollalong switch must be configured for K+N inputs and K outputs.

GL(+) Ground location numbers along the seismic line increasing numerically in the direction in which the active geophone array is advanced for each successive record sequence GL(-) Ground locations numbers decresing numeric ally in the direction in which the active spread is advanced.

CH(+) Seismic data channel increasing (1 to K) numerically along the active spread in the direction in which the active spread is advanced.

CH(-) Seismic data channels numerically decreasing (from K to 1) in the direction in which the active spread is advanced. 40 01 05 40 Note that the signs ( + ) (-) of each of the ground location numbers (GL) signifies its relationship with respect to the direction of the array advance; the reference sensor and the sign of the channel number are also dependent on the array reference status. If the latter is 1, the CH is positive. If not, then the sign is negative.

SEQUENCE START EQUATION SET II With the ground location numbers increasing but the channel numbers decreasing, the following set of equations is used : (1) RLSP = TR-REF-GPNO+1 (2) END 1 = REF+GPNO+K-1 (3) END 2 = REF If GPNO = 0 (4) GAP 1=0 (5) GAP 2=0 If GPNO > 0 (4) GAP 1 = END 1-GPLOC-1 (5) GAP 2 = END 1-GPLOC-GPNO (6) ROOM = TR-REF-GPNO.

SEQUENCE START EQUATION SET III With ground location numbers decreasing but the channel numbers increasing, the following set of equations is used : (1) RLSP (2) END 1 (3) END 2 If GPNO (4) GAP 1 (5) GAP 2 If PPNO > 0 ( 4) GAP 1 (5) GAP 2 ( 6) ROOM TR+NP-REF REF REF-(K-l)-GPNO 0 0 0 REF-GPOC-1 REF-GPLOC-GPNO REF-TR-GPNO+1 SEQUENCE START EQUATION SET .IV With both ground location numbers and channel numbers decreasing, the following set of equations is used: (1) RLSP (2) END 1 (3) END 2 If GPNO = 0 (4) GAP 1 (5) GAP 2 If GPNO > 0 (4) GAP 1 (5) GAP 2 ( 6) ROOM REF-TR-GPNO+1 REF-(K-l)-GPNO REF 0 0 END 1+GPLOC-l END 1+GPL0C+GPN0 REF-TR-GPNO Following these operations, the operator peruses the data at displays 27 and the encoders 26. If it is correct, he activates the trigger switch 61 (FIG. 4) to ultimately cause the energy source 16 (FIG. 1) to be activated. But before that can run, there is transference of all pertinent header data to the digital field recorder 21 in the manner of FIGS. 8 and 10. Note in FIG. 10, that after the operator activates the firing switch 61, the DFS 10 generates a series of commands to the recorder 21 which executes them in the manner shown. I.e., the tape drive of the recorder 21 first accelerates the tape past the recording head until nominal operating speed is achieved. Then, regular header data is recorded on the tape at time T^-T2 • Note at time T2, the data associated with selected encoders 26 and displays 27 are next transferred in the manner depicted in FIG. 8 in which I/O array 34 enables the above "selected" elements to pass the associated data. That is to say, array 34 is capable of enabling displays 70-73 and encoders 48-53 so that data can be transferred via bus 80 and header interface 81 to th<5 recorder 21. Address multiplexer 78 is used to generate the prerequisite format in conventional 01 -20- fashion. As a result, annotation of spread and source position associated with subsequently collected seismic 05 data, is assured. (Note from FIG. 9E that the controller 20 is placed in an inhibited mode of operation during the recording of header data. Thus, if there are inadvertent changes in the controller status during the recording thereof, they do not affect operations.) 10 It should be noted that the address multiplexer 78 preferably formats the data using standard guidelines adopted by the SEG Technical Standards Subcommittee on Tape Formats, in the manner of FIG. 7.

DATA ARRANGEMENT AT RECORDER 21 15 As shown in FIG. 7, header segment 79 has 2x2 array dimensions that are sixty-four (64) bytes by nine (9) characters wide. Organization of each byte include two 4-bit BCD segments utilized to indicate: line direction, group interval, shot depth, shot offset, offset 20 direction, charge size, shot location, shot number, truck location, end group location, gap groups locations and associated data channel, in the order shown. As a result, adequate documentation of spread and source locations for annotation purposes, is assured.

It should be understood that the invention is not only directed to the specific embodiments set forth above, but that many variations are readily apparent to those skilled in the art, so thus the invention is to be given the broadest possible interpretation within the 30 terms of the following claims. 40 197637

Claims (13)

WHAT WE CLAIM IS:

1. Method of calculation, storing and recording positional data associated with a digital exploration system during generation and collection of seismic data by a source-detector array positioned at known locations along a line of survey, said positional data being generated as bits of digital data stored In a microcomputer system Including a microprocessor unit (MPU), memory units, and a series of display/storage and switching devices Interconnected to each other and to a digital field system (DFS) via a system bus, whereby errors In exploration activities are reduced, and annotation of exploration activities Is automatically added, comprising; (a) establishing In digital format via said microcomputer system, array geometry and exploration parameters that allow annotation In sequence of exploration activities along said line, (b) automatically display Ing at said dIspI ay/storage and switching devices of said system, at least a portion of data of (a) In alpha-numeric form for operator examination and correction, If required, and (c) automatical Iy recording said portion of data of (a) as header data so as to provide full annotation of exploration activities whereby errors In such exploration activities can be discovered and accounted for.

2. Method of claim 1 In which (c) Includes applying clocking and trigger signals to said dIsplay/storage and switching devices whereby stored data Is systematically accessed and recorded as header data.

3. Method of claim 1 In which step (c) Is Initiated by actlvatlngva^ h firing sequencing switch whereby a recorder unit of said DFS Is energ 1^41.4^^ and after Its generation is stab 11 zed, said header data Is recorded to provide annotation of said activities. - 22 - 197637

4. Method of claim 3 In which said activation of said firing switch also provides for subsequent activation of a seismic source of said source-detector array whereby generated waves propagate through an earth formation beneath said source-detector array and after detections by detectors of said array, are also recorded by said recording unit of said DFS.

5. Method of claim 3 in which said Vecorder unit arranges said data In a convenient format Including recording Information associated with truck position along said line, reference location of said array, shot location along said line, gap position along said line, gap number, rollalong number, shot occurrence count, end position of said array, and channel recorder count.

6. Method of calculating, storing and recording positional data associated with a digital exploration system during generation and collection of seismic data by a source-detector array positioned at known locations along a line of survey at the earth's surface, said positional data being generated as bits of digital data In a microcomputer system Including a microprocessor unit (MPU), memory units and a series of dI splay/storage and switching devices Interconnected to each other and to a digital field system (DFS) via a system bus, whereby errors In exploration activity — both pre-actlvatlon and past-release of energy fron said source — are substantially reduced} comprising: i (a) encoding and automatically storing additional digital data related to array geometry and exploration parameters that allow rep^Hl^rfT^ r In sequence of activities along said line, i\N (b) automatically displaying at least a portion of said enco &7 MAR 1986 ntj data In alpha-numeric form for operator examination and for correctly If required, - 23 - 197637 (c) automatically generating via said microprocessor system further additional data related to array parameters based in part on data encoded at (a), and previously stored data related to exploration parameters, (d) displaying at said display/storage and switching devices of said microcomputer system at least a portion of said new array parameters of (c) for operator examination and correction, If required, and (e) automatically recording portions of said displayed data of steps (b) and/or (d) as header data so as to provide full annotation of exploration activities whereby errors In such activities can be pinpointed and taken 1nto account.

7. Method of claim 6 In which step (c) is Initiated by activating a firing sequencing switch whereby a recorder unit of said DFS is energized and after Its operation is stabilized, said header data Is recoJ?ae if*;provide annotation of said activities. If /;r\ 5;

8. Method of claim 7 In which said activation of said f irIngx^(/tc^ al provides for subsequent activation of a seismic source of said source-detector array whereby generated waves propagate through an earth formation beneath said source-detector array and after detection of said array, are also recorded by said recorder unit of said DFS.;

9. Method of calculating, storing and displaying positional data, associated with a digital exploration system during generation and collection of seismic data by a source-detector array positioned at known locations along a line of survey at the earth's surface, said positional data being generated as bits of digital data in a microcomputer system Including a microprocessor unit (MPU), memory units and a series of display/storage devices interconnected to each other and to a digital;- 24 -;197637;field system (DFS) via a system bus, whereby errors in exploration activity — both pre-activatlon and past-release of energy from said source — are substantially reduced, comprising:;(a) encoding and automatically storing additional digital data related to array geometry and exploration parameters that allow repetition In sequence of activities along said line,;(b) automatically displaying at least a portion of said encoded data In alpha-numeric form for operator examination and for correction, If requI red,;(c) automatically generating via said microcomputer system further additional data related to array parameters based in part on data encoded at (a), and previously stored data related to exploration parameters, and;(d) displaying at said display/storage devices of said microcomputer system at least a portion of said new array parameters of (c) for operator examination and correction, if required, whereby err£ in exploration activities can be substantially reduced, prior to activation of said source of said array. |®;

10. Method of claim 9 In which (a) Includes encoding as bits of digitaT~i*~' data In said microcomputer system truck, source and array positions vls-a-vis said known geographical positions along said line of survey.

11. Method of claim 9 with the additional steps of (i) assuming that the displayed data of steps (b) and (d) meet with operator approval transmitting a firing command to said DFS whereby seismic waves are generated by said source and propagate through an earth formation and In wlhlch reflections of said generated waves are detected by said array of detectors, followed finally by recording indications of said received waves at a recording unit of said DFS, - 25 - 197637 (II) In response to a generated command signal, recaluclatlng next-In-line array and source positional parameters for operator approval using said MPU of said microcomputer system, (III) displaying said parameters of (II) for operator examlnat.

12. Method of claim 9 In which (b) Includes alpha-numeric displays of said positional data at said dI splay/storage devices, so as to depict truck position along said line, reference location of said array, shot location along said line, gap position along said line, gap number and rollalong number.

13. A method of calculation, sorting and recording positional data associated with a digital exploration system during generation and collection of seismic data substantially as hereinbefore described with reference to the accompanying drawings. fty Ws/their authorised k i & SON.