GB2248499A - Seismic data interpretation digitising scanner - Google Patents

Abstract

An automated scanner for the digitisation of interpreted data on seismic sections, comprising a powered document transport system, a computer processing unit (C.P.U.) 42, and a scanner head 32 consisting of a linear illuminator 12 and sensor elements 14. The data interpretations are drawn on a seismic section 10 using ultra-violet sensitive wax crayon pencils, and the section is transported beneath the scanner head where the wax is illuminated by ultra-violet light and ultraviolet fluorescence is detected by the sensor elements. A single scan of the seismic section will therefore detect all interpretations on the section. The data are then processed by the C.P.U. and converted into digital signals, which are transferred to external computer devices for further data processing or stored internally. <IMAGE>

Description

SEISMIC DATA INTERPRETATION DIGITISING SCANNER This invention relates to a scanning device for digitising interpreted seismic sections by automated means.

Seismic data surveying is the Petroleum Industry's main tool for use in the search for hydrocarbons. The results of a seismic survey are usually presented as paper records or seismic sections which are suitable for use in data interpretation. Seismic data interpretation is normally conducted on the paper sections by identifying and marking out, using coloured pencils, individually correlated seismic events. These events are pressure wave travel time representations of geological formation interfaces or surfaces within the Earth's crust.

When the correlation of the various seismic events is thus completed throughout a survey data set, the structural form of each colour-marked or picked interface is defined by digitising relative arrival times and distance from specified origins on each seismic record. These multi-section survey, time and scaled distance values are then mapped in combination to generate three-dimensional structural contour representations of geological surfaces in depth, in order to outline likely hydrocarbon traps.

The introduction of computers in the oil industry has made possible the digitisation of interpreted seismic data for use in computer based sub-surface mapping. Currently, interpreted seismic sections are digitised using manually operated digitising tables.

The mode of employment of present day models involves a substantially laborious and repetitive digitising set-up of individual seismic sections, whereby the definition of the time and distance origins and the seismic picked events is made by discrete digitising steps using an attached cursor. The digitised point values are stored in a computer memory for later data manipulation and use in standard mapping software packages.

Over the last decade, the use of digitising tables to digitise interpreted seismic data has contributed much to speeding up the interpreter's operations in sub-surface mapping, yet most of the ground work conducted in this field remains essentially manual. Manual intervention in data digitising must, by virtue of human nature and the large volumes of data usually involved, invariably lead to the introduction of errors and inaccuracies into the mapping data sets. Manual digitising often proves to be costly in terms of manpower and is both time and tmancially consuming to conduct and correct.

This invention is thus devoted to describing a specification for a design that would allow for an accurate, fast and operationally simple automated means for digitising interpreted seismic sections which eliminates the human factor.

According to the present invention there is herein provided a seismic data interpretation digitising scanner whose basic working principle is dependent on the detection of one of a number of physical properties pertaining to a coloured pencil wax. One such system would be based on detecting the light emission property of a crayon wax containing an ultra-violet sensitive substance, after excitation by ultraviolet light.

The specification for this invention would provide for a seismic data interpretation digitising scanner, which is comprised of six basic elements:1. An ultra-violet light source 2. A document transport system 3. An emitted light sensing element 4. A computerised transport control system 5. A computerised signal threshold processing system 6. A computerised data storage and/or data transfer facility A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1, a schematic drawing showing in perspective the digitising scanner in working mode.

Figure 2, a schematic side elevation section through the scanner showing the computer processing unit, document transport system, the ultra-violet source, light emission sensor and scanning head within the scanner casing.

Figure 3, a schematic side elevation section through the opposite end of the scanner showing the document transport drive motor and roller arrangement of the system.

Referring to the drawing, the scanner comprises a multi-roller arrangement document transport system which serves to position the seismic section, 10, in front of the source, 12, and sensing elements, 14, collectively termed "scanning head", all suitably contained within a supported rigid metal casing made up of a lower, 16, and upper, 18, half (Figures 1 and 2).

The lower casing half of the scanner, 16, supports a document guide tray 20 and houses three adjacent equi-sized rollers 22, 24, 26 whilst the opening top 18 internally supports two sets of small twin rollers, 28 and 30, placed either side of the source and sensor head, 32. The position of these upper twin roller sets, 28 and 30, is designed such that contact is made with the lower front, 22, and back, 26, large rollers when the top, 18, is closed. A motor, 34, located within an isolated end casing, 36, at the lower left end of the scanner (Figure 1) drives all lower and upper case rollers, 22, 24, 26, 28 and 30, at the same speed when the top, 18, is closed and the instrument is running (Figure 2). The direction of document movement within the device is dictated by the roller system rotation direction and is as indicated by the arrows shown in all Figures.

The scanning head, 32, is constructed from an insulated light alloy or other suitable material, and is divided into two separately isolated longitudinal chambers, 38, 40.

The chamber, 38 adjacent to the upper lead or feeding roller set, 28, houses a longitudinal high intensity ultra-violet light source, 12. The chamber, 40, adjacent to the trailing or extractor roller set, 30, houses a longitudinal light sensing element or charge coupled device array (CCD), 14, (Figures 2 and 3).

When the interpretation of a seismic section is completed using the special wax coloured pencils and is required to be scanned, the vertical time and horizontal distance minimum and maximum scale values are first marked as reference points using the special pencils. Where the data has already been interpreted using normal coloured pencils, both the interpretation and reference points must be overdrawn using the special light sensitive pencil.

The section, 10, is then placed on the guide tray, 20, and inserted into the document transport, where it is gently pinched between the front set of upper, 28, and lower, 22, rollers, and fed under the scanning head, 32. The centre lower roller, 24, holds the document, 10, close to the head, 32, and provides support while the section is thus passed to the back set of upper, 30, and lower, 26, rollers which carry the document, 10, out of the back of the scanner (Figures 1, 2 and 3).

When a part of the section, 10, passes beneath the excitation source, 12, the coloured pencil pigment will selectively fluoresce to the exclusion of the section background.

The fluorescence of the special pencil wax will be detected by the sensor, 14.

The light sensing element, 14, could be made up of commercially available Charge Coupled Device arrays (CCD's). These accumulate electrical charges that are equal to the amount of light transmitted onto them. Each CCD contains an array, or longitudinally organised collection, of light sensing elements. The linear array of elements (picture elements or pixels) in the CCD is used to accurately scan the whole width of the section, 10, at the same time, thus simultaneously covering all the picked seismic events interpreted on the section.

Normally, document scanning would sense light arriving at the CCD from both the background data as well as the picked events. The objective of this design is to collect information from the interpreted picks only, which overcomes unnecessary design complications arising from handling and editing huge amounts of information otherwise generated. This mode of selective scanning will thus register the position of each of the picked events relative to the vertical time and horizontal distance reference points, and scans will progressively be made at regular intervals along the section, as it is fed through.

The registration of the data for each successive scan is controlled by a computer processing unit or board (CPU), 42. This board is contained within a separate housing, 44, at the right hand end of the device and is accessed by a control panel, 46, suitably sited for easy operator use (Figures 1, 2 and 3). The CPU has two basic functions. Firstly, as a transport control system, it is responsible for controlling the speed of the motor, 34, to ensure scanning in continuous or stepped motion and, secondly, as a signal threshold processing system.

Once the data from each scan has been extracted, the CPU, 42, is then used to convert these data to a storable or transferable form and will convert the analogue signal to a representative digital form (A to D conversion). The threshold at which the analogue signal is turned into a digital value can either be set manually on the control panel, 46, or can be set automatically by the CPU, 42.

When converted to digital format, the data from each scan can then either be transferred to a suitable storage device, such as an internal floppy or hard disk or is made available at a digital interface, 48, (Figure 1) for transfer to an external device.

Since all the reference points on the section and all the seismic picks can thus be recorded by the scanner, further processing on a remote computer system will transfer the information into a standard data format that can be used by industry standard computer systems. The processing would include the details of the reference points as well as the renaming of each of the seismic events. This information could, if necessary, be included with the stored information by the provision of an alphanumeric keypad as part of the scanner control panel, 46.

Claims (6)

1. An automated scanner for digitisation of interpreted data on seismic sections comprising a multi-roller powered document transport system to provide means of moving a seismic section under a scanning head consisting of an ultra-violet light element serving as an excitation source for seismic data interpretation made using special crayon pencils containing an ultra-violet sensitive substance in the pigment and a linear Charge Coupled Device array which acts as an emitted light sensor for simultaneous progressive scanning of all data interpretations on the seismic section; a computer processing unit to control the document transport system and provide a means of performing analogue to digital data conversion and signal threshold processing to the digital data output and a means of digital data transfer to other external computer devices for further data processing.

2. An automated scanner for digitisation of interpreted data on seismic sections as claimed in Claim 1, wherein the digital data output are directed to storage on a computer disk internal to the device.

3. An automated scanner for digitisation of interpreted data on seismic sections as claimed in Claims 1 and 2, wherein the light sensing element (CCD) is constructed from a number of smaller overlapped CCD units to form a linear sensor array.

4. An automated scanner for digitisation of interpreted data on seismic sections as claimed in Claims 1 and 2, wherein the light sensing element (CCD) is so constructed to directly detect coloured light transmitted from the crayon waxes within the visible light frequency spectrum. The illumination source in this case would be ordinary white light.

5. An automated scanner for digitisation of interpreted data on seismic sections as claimed in Claims 1 and 2, wherein the light sensing element (CCD) is so constructed to enable detection of surface reflection contrast of wax on paper. The illumination in this case would be ordinary white light.

6. An automated scanner for digitisation of interpreted data on seismic sections as claimed in Claims 1 and 2, wherein the sensor is constructed of a video camera which includes a CCI) as an integral part. In this case the interpreted data image is gathered through the camera.