SYSTEMS AND METHODS FOR PLANNING SEISMIC DATA ACQUISITION WITH REDUCED ENVIRONMENTAL IMPACT

Abstract

The invention relates to systems and methods for designing seismic surveys to enable seismic data acquisition with a reduced environmental impact and lower survey costs. The methods include incorporating surface and subsurface data and associated parameters for a proposed survey area and assigning weighting values to the relative ranking of the parameters for a particular area and thereafter designing a source/receiver plan based on combined and weighted parameters.

Claims

1: A seismic survey design method comprising the steps of: for a defined land and/or marine area: a) obtaining two or more data sets for the defined land and/or marine area wherein each data set includes relative ranking values for sub-zones within the defined area; b) over-layering two or more data sets; c) for a defined resolution of the over-layered data sets, applying a weighting factor to each relative ranking value for each data layer and summing weighted ranking values across all over-layered data sets to determine a combined weighted ranking value for the resolution.

2: The method as in claim 1 further comprising the step of filtering combined weighted ranking values into two or more categories and applying different survey geometries to each category.

3: The method as in claim 2 wherein survey geometries are applied to correlate larger combined weighted ranking values to a survey geometry having less disturbance as compared to smaller combined weighted ranking values to a survey geometry having more disturbance.

4: The method as in claim 3 wherein the survey geometries are applied to correlate larger combined weighted ranking values to a survey geometry having fewer sources and receivers as compared to smaller combined weighted ranking values to a survey geometry having more sources and receivers.

5: The method as in claim 2 wherein the survey geometries are selected from survey geometries including: a) orthogonal and separate source and receiver lines having intersecting lines between the source and receiver lines; b) non-linear source and receiver lines having non-intersecting lines between adjacent non-linear lines; and wherein the survey geometries are ordered from least sensitive to most sensitive.

6: The method as in claim 2 further comprising the step of creating a survey design for the defined area, the survey design having a plurality of survey geometries applied to different sub-zones of the defined area.

7: The method as in claim 1 further comprising the step of filtering the survey design to reduce complexity of transitions from one survey geometry to another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Various objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention. Similar reference numerals indicate similar components.

[0029] FIG. 1 is a flowchart showing seismic survey planning steps in accordance with one embodiment of the invention;

[0030] FIG. 2 is a schematic representation of a proposed survey area showing two layers (A) and (B) of environmental data;

[0031] FIG. 2A is a schematic representation of a proposed survey area showing two layers (A) and (B) of environmental data overlaid with one another.

[0032] FIG. 2B is an example of overlaid environmental data in a real-world example.

[0033] FIGS. 3 and 3A are an example of a base survey design.

[0034] FIGS. 4 and 4A are an example of an alternate geometry design showing non-orthogonal seismic lines.

[0035] FIG. 5 is a schematic representation of the process by which weighting factors are applied to different layers of environmental data.

[0036] FIG. 5A is an enlarged view showing assigned area rankings based on applied weighting factors.

[0037] FIG. 5B is an example of layer combination in a real-world example.

[0038] FIG. 6 is an example of a real-world survey design after filtering.

[0039] FIGS. 7 and 7A are schematic representations of the application of different survey designs applied to a survey area after weighting.

[0040] FIG. 7B is an example of different survey designs applied to a real-world example with an enlargement showing transitions between different survey designs.

DETAILED DESCRIPTION

[0041] With reference to the figures, systems and methods for seismic survey planning and implementation are described. The systems and methods described enable improved survey planning and design of seismic surveys to reduce the environmental impact of acquiring seismic data in survey areas including sensitive ecological environments and/or reduce the cost of acquiring seismic, while matching or exceeding the resulting data quality of a conventional seismic program. Specifically, the systems and methods enable the design of surveys that provide for a reduction in the total cut area and the linear distance of cut-lines in a program area compared to conventional LIS seismic.

[0042] Various aspects of the invention will now be described with reference to the figures. For the purposes of illustration, components depicted in the figures are not necessarily drawn to scale. Instead, emphasis is placed on highlighting the various contributions of the components to the functionality of various aspects of the invention. A number of possible alternative features are introduced during the course of this description. It is to be understood that, according to the knowledge and judgment of persons skilled in the art, such alternative features may be substituted in various combinations to arrive at different embodiments of the present invention.

[0043] The systems and methods are described by a representative example of the process of designing a survey. As shown in FIG. 1, a seismic survey is designed through the following general steps and as described below. These include environmental and other surface and/or subsurface data input 100, base survey design 101, alternate geometry design 102, layer combination 103, rank filtering 104, additional filtering 105, survey layout 106 and station renumbering 107.

Step 100Acquire Environmental Data for a Region

[0044] As shown in FIG. 2, a land area 20 to be surveyed is shown schematically. The boundary of the survey area is the outer perimeter 20a. The survey area includes a number of different zones shown as various polygons in FIGS. 2(A) and 2(B).

[0045] FIG. 2(A) shows a first layer of one type of environmental and/or other surface/subsurface data and FIG. 2(B) shows a second layer of another type of environmental and/or other surface/subsurface data, indicated as polygons within the same perimeter 20a.

[0046] For example, FIG. 2(A) may be illustrating disturbance layer data whereas FIG. 2(B) may be illustrating caribou calving sensitivity data. Each layer is shown divided into zones, with FIG. 2(A) showing 6 different disturbance zones as polygons within the perimeter 20a and FIG. 2(B) showing 3 different zones within the same area. Each zone is shown with a different sensitivity number or ranking number where a higher number is representative of greater environmental sensitivity or a relative ranking for that particular layer parameter.

[0047] For example, there are 6 marked zones in FIG. 2(A) with shown sensitivities 1A, 2A, 3A, 4A, 5A and 7A. Zone 1A is the least sensitive zone whereas Zone 7A is the most sensitive. As an example, Zone 1A may be a forested area of predominantly aspen trees whereas Zone 7A may be a fen (i.e. an environmentally sensitive wetland). Generally, certain forested areas may be less sensitive than a fen in terms of the ability to recover from an intrusion with survey personnel/equipment for source and receiver placement. That is, aspen trees are known to grow back rapidly when cut whereas a fen may take many decades to recover from an intrusion.

[0048] Zones 2A, 3A, 4A, 5A are areas with intermediary sensitivities, for example, 2Aconiferous forest, 3Adeciduous forest, 4Ashrub land and 5Agrassland and so on.

[0049] Similarly, as shown in FIG. 2(B), 3 zones are illustrated namely, 4B, 7B and 12B showing caribou calving sensitivity data with the numbers representing increasing sensitivity. For example, zone 12B may be a zone where caribou are known to seasonally calve and therefore known to be an area of high sensitivity whereas the other zones are known to be less likely to see caribou calving.

[0050] Various types of environmental, surface, or subsurface data may be considered to include, but not limited to: [0051] Vegetation regrowth potential [0052] Seasonal or permanent wildlife presence/activity. [0053] Number of species present [0054] Waterways or other sensitive areas [0055] Previously disturbed areas [0056] Undisturbed areas [0057] Greenhouse gas emission potential [0058] Subsurface target zones of interest

Step 100AOverlay Data

[0059] In step 100A, the different data/zones are overlaid on one another such that the polygons of each layer are overlaid with one another as shown in FIG. 2A. Such data is typically imported in shapefile format, but may be in other geographical information systems (GIS) formats.

[0060] Each data layer may be supplied from a range of sources where the different zones for that particular data type use different scales to represent different levels of sensitivity or ranking. Step 100A, will generally also normalize the scale range for each data layer, such that the number used to describe ranking is normalized to a common scale for each data layer. For example, layer 2 depicts one zone with a 12 ranking. Thus, if it is desired that the ranking scale across all layers is 1-10, the layer 2 data would be normalized to a scale of 1-10 where the ranking number 12B (which may be the highest ranking number for that data type) would be adjusted to, for example, 10B as shown in FIG. 2A.

[0061] Accordingly, in this example, the highly sensitive calving zone 12B is overlaid with moderately sensitive regrowth zones 7A, 5A, 4A and low sensitivity area 2A.

[0062] A representative example of real-world data with multiple layers of data is shown in FIG. 2B which depending on the number of layers being implemented can be complex.

Step 101Create Base Survey

[0063] As shown in FIGS. 3 and 3A, initially, a base survey plan is created for the survey area in which a standard survey of sources 12 and receivers 14 is laid out in an orthogonal grid. As shown, the source lines 12 run east-west and the receiver lines run north-south and represent/illustrate the cut-lines that would be required to conduct a standard survey. The spacing between parallel cut-lines and the number sources and receivers along each cut-line can be adjusted as can the configuration of the lines (continuity, angle, regularity, etc.). Other base survey layouts may be slant or megabin and/or any other conventional geometry.

[0064] The base survey plan as shown in FIG. 3 does not take into account any environmental, surface, or subsurface data at this point. For the purposes of illustration, a cut-line XY would thus extend continuously from X to Y (e.g. east-west) and the cut-line AB would extend continuously from A to B (e.g. north-south) thus, providing clear passageway between each point if a corresponding cut-line was made. In addition, at cross-over points (e.g. C), there is clear passageway from one direction to another.

Step 102Alternative Geometry

[0065] As shown in FIGS. 4 and 4A, alternate geometries can be designed that prevent straight cut-lines across the area. In FIG. 4A, 50% of the source and receivers have been removed from the base survey such that the cut-lines form a zig-zag pattern across the area. For example, from point B to Y, a zig-zag cut-line is formed. The zig-zag cut-line may include various combinations of sources and receivers, for example a number of North-South aligned receivers may alternate with a number of East-West aligned sources with a 90 degree turn between each set. As such, the resulting zig-zags do not cross one another with the result being that there is undisturbed vegetation between each zig-zag which thereby reduces the length of all lines-of-sight and does not enable, for example, movement of wildlife from one zig-zag to the other without crossing undisturbed land. Thus, a comparison of the base survey design as shown in FIG. 3 and the alternative geometry design of FIG. 4, shows the effect of different cut-lines on the potential interaction of predators P (e.g. wolves) and non-predators NP (e.g. caribou). As shown in FIG. 3, predators P can sight from a longer distance along the cut-lines and also more readily move from predator location to non-predator location along a cut-line, whereas in FIG. 4, the predators cannot sight as far and must move through undisturbed land to get to the NP location. Predation advantages based on wind direction would also be diminished as wind energy would be scattered rather than channeled down cut-lines.

[0066] Alternate geometries will have affects on the total length of cut-lines and variations in the patterns of placing sources and receivers can be adjusted as well as the number of sources and receivers along given cut-lines. The final determination of the patterns and the sources and receivers may further take into account the effects of certain patterns and source/receiver numbers on the quality of the seismic data that is ultimately collected when the survey is undertaken.

[0067] Thus, a design as shown in FIGS. 4 and 4A provide advantages over a base survey design in terms of reduced number of lines, shorter line segments and may also include a smaller number of sources and receivers which will lead to reduced costs and environmental impact.

Step 103Apply Weighting Factors

[0068] As shown in FIGS. 5 and 5A, weighting factors are next applied to the overlaid data wherein each layer of data can be assigned a relative importance in comparison to other data layers. For example, in an area where the differences in environmental sensitivity may be relatively small, each layer of data may be assigned a substantially equal weighting. That is, in areas where there are little known/anticipated wildlife issues, and/or the absence of particularly sensitive land, each data layer may be considered as substantially equally important to each other.

[0069] In contrast, there may be a relatively important layer of data, for example, caribou calving data. FIG. 5 shows an example where the layer 1 data has been assigned a 75% weighting and layer 2 data has been assigned a 25% weighting such that for a given area (e.g. a 0.5 sq km resolution), the combination of the ranking of a particular zone in one layer is weighed and summed with the weighted sensitives for other data layers.

[0070] For example, as shown in Table 1, a weighted ranking for a given area is illustrated.

TABLE-US-00001 TABLE 1 Weighted Analysis for Defined Area Assigned Normalized Weighting to Weighted Ranking (A) Data Layer (%) Ranking Layer (Scale 1-10) (B) A * B 1 8 70 5.6 2 5 15 0.75 3 1 5 0.05 4 4 10 0.4 Total: 6.8

[0071] Upon determination of a weighted ranking, a defined number of ranges may be defined for the weighted sensitivities. For example, in the example of Table 1, 3 ranges may be defined, 0-2.5, >2.5-5, and >5 wherein each defined range is used to determine the geometry of the survey.

[0072] As shown in FIGS. 5 and 5A, weighted sensitivities are determined for a defined area within each zone wherein at the intersection of 3 zones as shown, a different value has been assigned for defined land areas wherein, in this case, 3's represent a more sensitive area that requires a more sensitive survey design, and 1's represent a less sensitive that enables a less sensitive survey design. Application of this analysis a real-world land area is shown in FIG. 5B.

Steps 104 and 105Filtering

[0073] As shown in FIG. 5B, the number of boundaries between proposed survey designs may be excessive; hence, filtering may be applied as shown in FIG. 6, where the resolution is decreased in order to decrease the relative complexity of the final survey design. Manual filtering may also be applied if an operator wishes to manually adjust the resolution based on their assessment of the particulars of a land area.

Step 106Finalize Survey Plan

[0074] As shown schematically in FIG. 7, plans for different survey designs are then applied to each zone. For example, if it was determined that polygons A-G were not sensitive areas, a base survey may be planned for those areas, whereas for polygons H-J, sensitive areas were identified wherein a zig-zag design may be appropriate and for polygons K-M, the most sensitive areas were identified wherein a survey design with less-impactful cut-lines is deemed to be appropriate. A final survey plan without polygons is shown in FIG. 7A and a representative final survey for a real-world area is shown in FIG. 7B.

Steps 107 and 108Station Renumbering

[0075] Finally, each source and receiver station may be renumbered to avoid numbering conflicts between stations within the different survey designs and may implement numbering based on a logical progression through different areas.

[0076] From this information about the native landscape and the environmental factors, the methodology: [0077] can be implemented to minimize the total amount of forest that is cut to accommodate seismic crews both in terms of linear kilometers and square kilometers. [0078] can be implemented to minimize the amount of interconnectivity through the survey area in order to make it more inconvenient for predators (and humans) to travel through the area when the area starts to regrow after the survey. [0079] can be implemented in non-forested areas to minimize the amount of disturbance to seismic equipment deployment. [0080] can be implemented to take account of immediate and future greenhouse gas emissions. [0081] can be implemented to reduce costs of acquiring seismic.

Other Features

[0082] In the design of a survey, it is important that the source/receiver density is adequate to image the subsurface target of interest. The base survey provides a starting point to selectively move/delete sources and receivers having consideration to the environmental and other surface/subsurface data.

[0083] Although the present invention has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the invention as understood by those skilled in the art.