METHOD OF FORECAST AND SEARCH OF HYDROCARBON DEPOSITS IN TRAPS OF ANTICLINAL TYPE BY TOPOGRAPHIC MAPS OF DAY SURFACE Russian patent published in 2014 - IPC G01V9/00 

FIELD: oil and gas industry.

SUBSTANCE: based on structural maps and seismic profiles, by earlier seismic exploration researches within the earlier studied sites of oil-and-gas province, stratigraphic interval down the geological section is determined, by which satisfactory spatial correspondence of day surface morphology to morphology of paleorelief lithostratigraphic (seismostratigraphic) horizons is clearly observed. Topographic maps of all scales from 1:25000 to 1:1000000 and in the same scales a plan of earlier found deposits (if any) throughout the whole territory of intended works are scanned. Study territory is sorted by topographic maps into sites by the degree of relative compartmentalisation of relief that is expressed by the width of watershed areas, which basically define day surface morphosculpture. At that, the width of watershed areas measured by many tens of kilometres and even over one hundred kilometres indicates prospectiveness of a site for search of giant and large hydrocarbon deposits. Sites, within which the width of watershed areas is characterised by values to the first tens of kilometres, are prospective for detection of mainly small and medium hydrocarbon deposits. Study territory is sorted into sites by relative relief height. At that, sites with relatively big relief height indicate relatively large surface relief amplitude by underlying lithostratigraphic units, which imply probability of discovery of hydrocarbon deposits with higher amplitude. Based on the results of territory sorting by indicated parameters, sites are identified prospective for discovery of giant, large, medium and small hydrocarbon deposits. A site is selected based on the results of conducted analysis, meeting the solving tasks, within which forecast and further search of corresponding hydrocarbon deposits will be carried out by topographic maps in scale of 1:25000. Values of long and short axes of earlier detected hydrocarbon deposits and values of their sums for each deposit are measured. Plans in scale of 1:25000 of all earlier detected hydrocarbon deposits within the studied oil-and-gas province, region or district are matched with a topographic map in the same scale in order to find out the degree of correspondence in the plan of contours of detected deposits with the contours of local positive forms of present relief. Based on the results of this match, earlier detected hydrocarbon deposits are sorted into three groups: deposits, which contours' position on the plan almost exactly matches the contour of their corresponding local positive forms of relief; deposits, which plan position is displaced to the distance not exceeding the half of the value of a corresponding linear dimension of day surface local positive form; and deposits, which plan position is displaced to the distance exceeding the value of a corresponding linear dimension of day surface local positive form. For each deposit of the last group, values of the sum of their linear dimensions are found; at that, maximum value of the sum of linear dimensions of a deposit is determined as "critical". A conclusion is made that for deposits, which value of the sum of their linear dimensions meets or below the critical value, forecast reliability by this method within the given territory is not enough. By topographic map, day surface local positive forms with a value of the sum of linear dimensions exceeding the critical value are detected. A conclusion is made that these local positive forms of day surface on the plan by regionally productive sediments are matched by about the same hydrocarbon deposits by linear dimensions, orientation and configuration. Area of forecast deposits is measures and values of forecast hydrocarbon resources in them are determined by set for each oil-and-gas province empirical dependence between deposits area and their reserves. Based on dimensions, configuration and orientation of short and long axes of detected positive forms of present relief, all parameters of search seismic profiles network are designed. At that, for giant and large anticlinal traps, dimension of seismic profiles parallel to the trap's long axis must make double dimension of the long axis of positive relief form, and dimension of seismic profiles parallel to the trap's short axis must make triple dimension of the short axis of positive relief form. For medium and small traps, dimension of seismic profiles parallel to the trap's long axis must make triple dimension of the long axis of positive relief form, and dimension of seismic profiles parallel to the trap's short axis must make five-times dimension of the short axis of positive relief form. At that, one part of seismic profiles is to be designed perpendicular to the short axis of a forecast deposit, and the other one perpendicular to its long axis. By designed network of seismic profiles, seismic surveillance is carried out for each of forecast hydrocarbon deposits. Structural maps are created by target reflecting horizons, based on which exploration wells are recommended and staked.

EFFECT: increased forecast reliability, decreased scope of prospecting works.

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