METHOD AND APPARATUS FOR INVESTIGATING AN AREA WITH RESPECT TO PRESENCE/ABSENCE OF PREDETERMINED GEOPHYSICAL SUBTERRANEAN PROPERTIES

Abstract: For investigating an area with respect to the presence or absence of a predetermined geophysical subterranean property, as especially with respect to the presence/absence of exploitable subterranean hydrocarbon deposits, signals emanating from subterranean underground are monitored without applying an investigation stimulus. Under a further aspect there is proposed, irrespective how signals emanating from subterranean underground and as monitored are generated, to perform on such signals a non-linear time series analysis so as to decide whether said predetermined geophysical subterranean property is present or not.

Description: Method and Apparatus for Investigating an Area with Respect to Presence/Absence of Predetermined Geophysical Subterranean Properties Background of the invention 1. Field of the invention This invention pertains to investigating an area with respect to presence/absence of at least one predetermined geophysical subterranean property. It is thereby especially directed on investigating such area with respect to presence/absence of subterranean hydrocarbon deposits, especially of exploitable ones . In the latter case advantage is taken from the fact that hydrocarbon deposits as a multiphase fluidic system in porous environment behaves highly non-linear in opposition to other geophysical subterranean properties. Nevertheless, and in its generality the present invention may be applied for investigating areas with respect to presence/absence of other predetermined geophysical subterranean properties than on that of subterranean hydrocarbon deposits . 2. Description of prior art For investigating an area with respect to presence/absence of at least one predetermined geophysical subterranean property, especially with an eye on finding exploitable subterranean hydrocarbon deposits, it is known to expose the underground to an investigation stimulus, be it of mechanical or be it of electromagnetic nature. The response of the underground system is analysed on the basis of a correlation response/stimulus. Thereby, we understand as an investigation stimulus, a stimulus which is applied to earth in an area under investigation, specifically for such investigation purposes in opposition to a stimulus which is applied to earth by any third parties activities as by machines operating in neighbourhood etc. or which is applied by nature as e.g. by the wave rhythm of sea. We further understand by correlation in its most general mean- ing any analysing method which makes a comparison between a stimulus and system answer . The system is the subterranean underground of the area under investigation. According to the US-A-4 904 942 the investigation stimulus consists of a seismic impact such as caused by a dynamite ex- plosion and the electromagnetic signal response is analysed by correlation with the stimulus as an indication of the existence of hydrocarbon deposits. According to the US 5 877 995 the investigation stimulus consists of an electric field which is generated by a power source, and, again by correlation, seismic response waves are analysed. Summary of the invention It is an object of the present invention to provide novel methods for investigating an area with respect to presence/absence of at least one predetermined geophysical subter- ranean property and, accordingly, novel apparatus, thereby providing for new and additional approaches for such investigation. The method and apparatus according to the present invention may be practised and applied respectively per se or in combination with prior art approaches for increasing reliability of investigation results. This is reached under a first aspect of the present invention by a method for investigating an area with respect to presence/absence of at least one predetermined geophysical subterranean property which comprises the steps of • monitoring mechanical and/or electromagnetic signals emanating from subterranean underground of an investigated area without applying an investigation stimulus; • analysing said signals; • comparing the result of said analysing with the result of an equal analysis of signals emanating from subterranean underground of at least one area with known presence of said property; • identifying presence or absence of said property at said in- vestigated area by the result of said comparing. Thereby, no investigation stimulus is used and thus possible influences of such investigation stimulus on the subterranean system being somehow unpredictable are excluded. Under a second aspect the above mentioned object is reached by the inventive method for investigating an area as was mentioned, but which comprises the steps of • monitoring mechanical and/or electromagnetic signals emanating from subterranean underground of an investigated area; • analysing said signals by means of a non-linear time series analysis; • comparing the result of said analysing with the result of an equal analysis of signals emanating from subterranean underground of at least one area with known presence of said property; • identifying presence or absence of said property at said investigated area by the result of said comparing. With respect to non-linear time series analysis as exploited under one aspect of the present invention we refer to (1) H. Kantz and T. Schreiber "Nonlinear time series analysis", Cambridge University Press, Cambridge U.K., 1999, further to (2) R. Badii and A. Politi "Complexity", Cambridge University Press, Cambridge U.K., 1997 as well as to (3) T. Bohr et al . "Dynamical Systems Approach to Turbulence", Cambridge University Press, Cambridge U.K., 1998. With respect to the ath- ematic approach to such non-linear time series analysis we es- pecially and completely refer to that literature (1) to (3) which is to be considered as an integrated part of the present description with respect to such analysis technique as well as to the enclosed (4) Appendix A: R. Hegger et al . "Practical implementation on nonlinear time series methods: The TISEAN package", Chaos, Vol. 9, No. 2, June 1999, pages 413 to 435. In a preferred mode of the invention the method of performing a non-linear time series analysis as mentioned above is combined with the approach of applying no investigation stimulus. In a preferred mode of the inventive methods whereat analysing is performed on the basis of said non-linear time series analysis, deterministic and stochastic signal components from the monitored signals are neglected or separated and the deterministic-chaotic components are extracted and applied to the subsequent comparing. This may be accomplished e.g. using non-linear filtering such as described in (1) . Thereby, it must be noted that comparing may clearly be done by an engineer or, more generically, by a person who knows how a respective signal must look like if the predetermined property is present at the investigated area. Further, deterministic signal components are components of low dimension, deterministic-chaotic components are components of higher dimension (see (1) to (4) , latter enclosed) . As was mentioned above the inventive methods are preferably performed by selecting the predetermined subterranean property to be investigated on its presence or absence to be that of exploitable subterranean hydrocarbon deposits . In a further preferred mode of the inventive method analysing includes representing the signals analysed by at least one chaos indicator, thereby especially preferred by at least one of the following chaos indicators : - delay embedding - correlation dimension versus embedding dimension - structure function representation - Hurst-exponent-spectrum. Further, the inventive method's signal analysis preferably comprises either per se or - under the second aspect - in combination with the non-linear time series analyses, analysing the signals in their frequency spectrum representation. As was mentioned above under a first aspect the present invention proposes to monitor and analyse signals emanating from subterranean underground without applying an investigation stimulus. With respect to signals intrinsically emanating from the underground we refer e.g. to (5) N. Suda, K. Nawa and Y. Fukao "Earth's background free oscillations", Science 279: (5359), pages 2089 to 2091, 1998 and to (6) J. Vila, "The broadband seismic station CAD: Site characteristics and back- ground noise", Bull. Seismol . Soc . Am. 88/1, pp 297 - 303, 1998. So as to realise the object as mentioned above the present invention further proposes an apparatus for investigating an area with respect to presence or absence of at least one predetermined geophysical subterranean property. Under a first aspect the inventive apparatus comprises an arrangement of at least one transducer which senses mechanical and/or electromagnetic earth signals and generates at least one output sig- nal at an output. It further comprises an analysing unit, an input thereof being operationally connected to the output of the arrangement . The analysing unit generates at least one output signal without performing a correlation with a stimulus signal applied to the area. Thereby, the analysing unit does not perform any correlation with an investigation stimulus source signal, as e.g. stimulus response evaluation. Under the second aspect the inventive apparatus may or may not evaluate or co-evaluate by its analysing unit a stimulus sig- nal generated by an investigation stimulus source, and it does perform signal analysis by non-linear time series analysis as was defined above. Further, in the inventive apparatus the analysing unit generates an output signal in dependency of the deterministic- chaotic signal component of a signal applied to the input thereof . Further preferred embodiments of the inventive apparatus are defined in claims 10 to 15. Under a further aspect the present invention proposes a method for manufacturing a product with at least one component derived from natural hydrocarbon or being natural hydrocarbon as exploited from subterranean underground, said method compris- ing the steps of - monitoring mechanical and/or electromagnetic signals emanating from subterranean underground of an investigated area without applying an investigation stimulus; - analysing said signal ; - comparing the result of said analysing with the result of an equal analysis of signals emanating from subterranean underground of at least one area with known presence of exploitable subterranean hydrocarbon deposits ; - identifying presence or absence of said hydrocarbon deposits at said investigated area by the result of said comparing; - exploiting said subterranean hydrocarbon deposits of said investigated area if said comparing result identifies such presence and producing said product by said hydrocarbon exploited. Under the second aspect the present invention proposes a method for manufacturing a product with at least one component derived from natural hydrocarbon or being natural hydrocarbon as exploited from subterranean underground, said method comprising the steps of - monitoring mechanical and/or electromagnetic signals emanating from subterranean underground of an investigated area; - analysing said signals by means of a non-linear time series analysis ; - comparing the result of said analysing with the result of an equal analysis of signals emanating from subterranean underground of at least one area with known presence of exploitable subterranean deposits of hydrocarbon; - identifying presence or absence of said hydrocarbon deposits at said investigated area by the result of said comparing; - exploiting said subterranean hydrocarbon deposits of said investigated area, if said components result identifies such presence and producing said product by said hydrocarbon ex- ploited. Thereby, the possibilities opened by the inventive method and apparatus for investigation are exploited, which allows finding and thus exploitation especially of hydrocarbon deposits in a less costly way than was possible by prior art ap- proaches. This is especially due to the rather higher accuracy, which is gained by the present invention, especially when combined with prior art approaches. The invention will now be described by examples and with the help of figures. The figures show: Fig. 1: in a functional-block/signal-flow diagram an inventive apparatus of a preferred mode, operating according to the inventive methods and construed so as to perform steps of the inventive method of producing; Fig. 2: acoustical signals as monitored at an area without hydrocarbon deposits in the underground (a) and at an area (b) with hydrocarbon deposits present in the underground ; Fig. 3: delay embedding representation of the signals according to (a) of fig. 2, i.e. monitored at an area with no underground hydrocarbon deposits and (b) of the signal (b) of fig 2, i.e. of a signal monitored at an area with underground hydrocarbon deposits present; Fig. 4: correlation dimension as a function of embedding di- mension representation, namely (a) of signals (a) of fig. 2, i.e. as monitored at an area without underground hydrocarbon deposits and (b) of signals (b) of fig. 2, i.e. monitored at an area with hydrocarbon underground deposits present; Fig. 5: structure function representation (a) of signals according to (a) of fig. 2, i.e. as monitored at an area without underground hydrocarbon deposits and (b) according to (b) of fig. 2, i.e. of signals as monitored at an area with hydrocarbon underground depos- its present; Fig. 6: Hurst-exponent-spectrum representation (a) of signals according to (a) of fig. 2, i.e. as monitored at an area without underground hydrocarbon deposits and (b) of signals (b) of fig. 2, i.e. of signals as moni- tored at an area with underground hydrocarbon deposits present; Fig. 7: frequency representation (a) of signals (a) of fig. 2, i.e. as monitored at an area with no underground hydrocarbon deposits and (b) of signals (b) of fig. 2, i.e. as monitored at an area with underground hydrocarbon deposit present . According to fig. 1 acoustical and/or seismic and/or electromagnetic signals as do emanate from subterranean underground are monitored by means of an arrangement 1 of at least one of respective sensors or transducers. Thereby an investigation stimulus may or may not be applied. Under the first aspect of the invention it is not applied. As was mentioned, in a preferred embodiment a combination of geoseismic, acoustical and electromagnetic sensors is provided and operated in parallel . Such sensors are preferably spread over the area where a predetermined property as especially presence of hydrocarbon deposits is suspected. The outputs signals of the sensors are monitored synchronously. Additionally it may be advantageous to provide some or all of the sensors of the arrangement within boreholes in predetermined depth within the subterranean underground. It is further proposed to use sensors which may register signals with three separate components according to the three spatial directions. In a specific embodiment a sensor of the following type was used: • acoustical sensor • sensitivity: 10 "9 m/sec. • bandwidth: 0,1 - 16 Hz In fig. 2 the monitored acoustical signal at an area without subterranean hydrocarbon deposits (a) is shown, as well as (b) such signal recorded at an area with an exploitable deposit of hydrocarbon present in the underground. The signal as monitored at the output Ai of the arrangement 1 of transducers is led to the input E 3 of an analogue to digital converter arrangement 3. The digitalised signals at output A 3 of the analogue to digital converter arrangement 3 are fed to a signal versus time storage 5, wherein signal/time-sequences are stored. It is to be noted that the feed of signals from transducer ar- rangement 1 or from analogue/digital converter 3, or even from storage 5, finally to an analysing unit 7 may be done by any technique of signal-transmittance, e.g. by electric or optical connections or "manmade" by transportation of the signals stored as e.g. on tape or CD-ROM and input to the analysing unit. Further, the arrangement 1 may consist of one or more than one distinct transducer. Output signals of more than one transducer of arrangement 1 may be combined and pre-evaluated e.g. by averaging to form one signal finally input to analysing unit 7. In an embodiment as realised today signal sequences of 10 sec. to 60 sec. are stored in the signal versus time storage unit 5. The signal versus time sequences as stored in unit 5 are fed to the input E 7 of an analysing unit 7 performing - under the second aspect of the invention - a non-linear time series analysis . Preferably the analysing unit 7 separates from the signal versus time sequences input to E 7 deterministic signal components as well as stochastic signal components - if at all present in the input signals to a non-neglectable, disturbing amount respectively. Especially deterministic-chaotic signal components are further exploited. This exploitation of the deterministic-chaotic signal components is performed preferably in that signals indicative of such deterministic-chaotic components are generated in analysing unit 7. The signals input to E 7 or components thereof - thereby especially the deterministic-chaotic components - are represented by so-called chaos indicators . Such preferred chaos indicator signals as generated in analysing unit 7 are now shown, resulting from signals monitored as of (a) and (b) of Fig. 2. In fig. 3 signal according (a) of fig. 2, i.e. monitored at an area without hydrocarbon deposits, is shown in the so-called delay-embedded representation, as a chaos indicator. In (b) of fig. 3 the chaos indicator delay embedded representation of the signal according to (b) of fig. 2, i.e. monitored at an area with an exploitable hydrocarbon underground deposit present, is shown. In fig. 4 signal according to (a) of fig. 2, i.e. monitored at an area without exploitable hydrocarbon underground deposits, is shown with the chaos indicator correlation dimension versus embedding dimensions, whereas in (b) of fig. 4 this indicator is shown for signals of an area with hydrocarbon deposits present as of (b) of fig. 2. A third representation or chaos indicator of the signals as monitored, namely the Structure Function representation, is shown in fig. 5, resulting from the signal according to (a) of fig. 2 in (a) of fig. 5, i.e. monitored at an area without exploitable hydrocarbon underground deposit and, respectively, in (b) of fig. 5 according to the original signal (b) in fig. 2, i.e. with exploitable hydrocarbon underground deposit present . A still further and preferred chaos indicator, namely the Hurst-exponent-spectrum of the signals as monitored, is shown respectively in (a) and (b) of fig. 6. Course (a) results from signal (a) of fig. 2, i.e. from monitoring an area without hydrocarbon deposit, course (b) results from signal (b) of fig. 2, i.e. from monitoring an area with hydrocarbon deposit present in the underground. As shown in fig. 1 the analysing unit 7 preferably also performs a frequency spectrum representation on the signals input to E 7 . In a preferred mode both chaos indicator representation as well as frequency spectrum representation are exploited. In Fig. 7 the frequency spectra are shown of the monitored signals as of (a) and (b) of fig. 2, accordingly represented in fig. 7 (a) and (b) . At the output of the analysis unit 7 there appears the result of non-linear time series analysis of the signals monitored by the transducer arrangement 1 or of the deterministic-chaotic signal component in one or more than one chaos indicator rep- resentation. Thereby, the representations as of figs. 3 to 6 and their combinations are today preferred. Still following fig. 1 signals resulting from the non-linear time series analysis performed in analysis unit 7 and additionally preferred of FFT are led to a comparing unit 9. In a further improved embodiment, a storage unit 11 stores the same signal type of signals as output from the analysing unit 7, but from signals which have been monitored and analysed with the same apparatus as shown in fig. 1 at areas with predetermined subterranean property, especially with exploitable hydrocarbon subterranean deposits present. In comparing unit 9 the indicative signals output from unit 7 - the chaos indicators - especially prevailing from deterministic-chaotic signal components of signals at the input of unit 7 and - preferably - frequency spectra thereof are com- pared with the prerecorded respective signals stored in storage unit 11. At the output A 9 there is generated a signal as result of the comparison indicating if the area under investigation has a predetermined subterranean property especially if exploitable subterranean hydrocarbon deposits are present or not . It goes without saying that possibly such indication may directly be recognised e.g. on a screen at the output of the analyser unit 7, e.g. if the representation of Hurst-exponent- spectrum according to fig. 6 is exploited, which in fact allows direct interpretation of the output signal of analysing unit 7. By means of the preferred non-linear time series analysis and exploiting the deterministic-chaotic signal components, noise sources as of manmade noise and/or nature-made noise, e.g. generated by technical plants adjacent to the area monitored as well as purely stochastic noise may be filtered out. It has been recognised that especially the deterministic-chaotic signal components are most indicative for the presence of prede- termined structures and deposits and are most significant, especially for hydrocarbon deposits in the subterranean underground. By the fact that the inventive method and apparatus will improve identification of hydrocarbon deposits and will therefore significantly lower the price for finding such de- posits, it leads to a method for producing all kinds of materials with components derived from such naturally exploited hydrocarbon or directly of such hydrocarbon which products are significantly lower in overall production price compared with the same products manufactured exclusively with prior art methods and apparatus for finding subterranean hydrocarbon deposits .

Claims: Claims : 1. A method for investigating an area with respect to presence/absence of at least one predetermined geophysical subterranean property, comprising the steps of: • monitoring mechanical and/or electromagnetic signals emanating from subterranean underground of an investigated area without applying an investigation stimulus; • analysing said signals; • comparing the result of said analysing with the result of an equal analysis of signals emanating from subterranean underground of at least one area with known presence of said property; • identifying presence or absence of said property at said investigated area by the result of said comparing. 2. A method for investigating an area with respect to presence/absence of at least one predetermined geophysical subterranean property, comprising the steps of: • monitoring mechanical and/or electromagnetic signals emanating from subterranean underground of an investigated area; • analysing said signals by means of a non-linear time series analysis; • comparing the result of said analysing with the result of an equal analysis of signals emanating from subterranean underground of at least one area with known presence of said prop- erty; • identifying presence or absence of said property at said investigated area by the result of said comparing. 3. The method of claim 2, thereby monitoring said signals without applying an investigation stimulus. 4. The method of one of claims 1 to 3 , said analysing including neglecting or separating deterministic and stochastic signal components from said signals and extracting from said signals deterministic-chaotic components and performing said comparing including comparing said deterministic-chaotic compo- nents. 5. The method of one of claims 1 to 4, thereby selecting said predetermined subterranean property to be presence/absence of exploitable subterranean hydrocarbon deposits . 6. The method of. one of claims 1 to 5, said analysing includ- ing representing said signals and/or components of said signals by at lest one chaos indicator, especially by at least one of the following chaos indicators : - delay embedding - correlation dimension versus embedding dimension - structure function representation - Hurst-exponent-spectrum. 7. The method of one of claims 1 to 6, wherein said analysing comprises analysing said signals in their frequency spectrum representation. 8. An apparatus for investigating an area with respect to presence/absence of at least one predetermined geophysical subterranean property comprising: - an arrangement of at least one transducer sensing mechanical and/or electromagnetic earth signals and generating at least one output signal at an output; - an analysing unit, an input thereof being operationally con- nectable to said output of said arrangement and generating at least one output signal without evaluating a correlation with a measured investigation stimulus signal applied to said area. 9. An apparatus for investigating an area with respect to presence/absence of at least one predetermined geophysical subterranean property comprising: - an arrangement of at least one transducer sensing mechanical and/or electromagnetic earth signals and generating at least one output signal at an output; - an analysing unit, an input thereof being operationally con- nectable to said output of said arrangement and performing a non-linear time series analysis on a signal applied to said input . 10. The apparatus of claim 8, wherein said analysing unit per- forms a non-linear time series analysis on a signal applied to said input . 11. The apparatus of one of claims 8 to 10, said analysing unit generating at its output a signal representing at least one chaos indicator of a signal input to said input of said analysing unit. 12. The apparatus of one of claims 8 to 11, wherein said analysing unit generates an output signal in dependency of the deterministic-chaotic signal component of a signal applied to said input . 13. The apparatus of claim 11 or 12, wherein the output signal of said analysing unit represents at least one chaos indicator in at least one of the following representations: - delay embedding - correlation dimension versus embedding dimension - structure function - Hurst-exponent-spectrum. 14. The apparatus of at least one of claims 8 to 13 , wherein said analysing unit generates an output signal at its output representing a frequency spectrum of a signal input to the input of said analysing unit. 15. The apparatus of one of claims 8 to 14, further comprising a comparing unit, one input thereof being operationally connected to the output of said analysing unit, a second input thereof being operationally connected to the output of a storage unit, said comparing unit generating an output signal indicative of presence/absence of said at least one predetermined subterranean property of an area wherefrom said at least one signal input to the input of said analysing unit results from. 16. A method for manufacturing a product with at least one component derived from natural hydrocarbon or being natural hydrocarbon as exploited from subterranean underground, said method comprising the steps of - monitoring mechanical and/or electromagnetic signals emanating from subterranean underground of an investigated area without applying an investigation stimulus; - analysing said signal; - comparing the result of said analysing with the result of an equal analysis of signals emanating from subterranean underground of at least one area with known presence of exploit- able subterranean hydrocarbon deposits; - identifying presence or absence of said hydrocarbon deposits at said investigated area by the result of said comparing; - exploiting said subterranean hydrocarbon deposits of said investigated area if said comparing result identifies such presence and producing said product by said hydrocarbon exploited. 17. A method for manufacturing a product with at least one component derived from natural hydrocarbon or being natural hydrocarbon as exploited from subterranean underground, said method comprising the steps of - monitoring mechanical and/or electromagnetic signals emanating from subterranean underground of an investigated area; - analysing said signal by means of a non-linear time series analysis; - comparing the result of said analysing with the result of an equal analysis of signals emanating from subterranean underground of at least one area with known presence of exploitable subterranean hydrocarbon deposits; - identifying presence or absence of said hydrocarbon deposits at said investigated area by the result of said comparing; - exploiting said subterranean hydrocarbon deposits of said investigated area if said comparing result identifies such presence and producing said product by said hydrocarbon exploited.

Inventors: DANGEL STEFAN, RODE ERNST DIETRICH, SINGER JOHANNES, DANGEL, STEFAN, RODE, ERNST, DIETRICH, SINGER, JOHANNES
Applicants: ADNR TECHNOLOGY SERVICES GMBH, DANGEL STEFAN, RODE ERNST DIETRICH, SINGER JOHANNES, DANGEL, STEFAN, RODE, ERNST, DIETRICH, SINGER, JOHANNES
Application year: 2000
Main classification: G01V1
IPC codes: G01V1