Prospecting technique

• US 6,560,537 B1
• Filed: 04/20/2000
• Issued: 05/06/2003
• Est. Priority Date: 04/21/1999
• Status: Expired due to Fees

• Current Assignee: Noranda, Inc. (Glencore Plc)
• Original Assignee: Noranda, Inc. (Glencore Plc)
• Inventors: Matthews, Larry
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): Taylor, Victor J.
• Application Number:
  US09/557,006
• Time in Patent Office: 1,111 Days
• Field of Search: 367/69, 367/73, 324/305, 702/16, 702/6, 702/2, 702/10, 702/14, 703/10
• US Class Current: 702/2
• CPC Class Codes: G01V 1/00 Seismology; Seismic or acoustic prospecting or detecting

Abstract

Disclosed herein is a technique of prospecting for deep massive sulphide ore bodies, comprising the steps of selecting a geologic region which is substantially acoustically transparent; directing seismic waves at the region and collecting reflected or diffracted waves therefrom; and analyzing the collected waves for the presence of the massive sulphide ore bodies.

Claims

1. An exploration process for evaluating a plurality of geological regions which are candidates for massive sulphide deposits, comprising the steps of:

(a) obtaining impedance characteristics for corresponding strata located in a selected one of said geological regions;

(b) analyzing the impedance characteristics for determining the presence of impedance transitions from one of the strata to another;

(c) validating the presence of a host lithology in said strata of the selected region based on said impedance transitions by determining whether said host lithology is substantially acoustically transparent, such that the host lithology is represented by a seismic profile which contains a substantial absence of impedance markers of magnitude greater than that of any survey noise present in said impedance characteristics; and

(d) confirming the selected region possesses a host stratigraphy that is substantially acoustically transparent and is therefore a candidate for a subsequent seismic investigation for massive sulphide deposits.

2. A method of exploration for evaluating a plurality of geological regions for the suitability of direct detection of a massive sulphide deposit, the method comprising the steps of:

(a) obtaining impedance characteristics for corresponding strata located in a selected one of said geological regions;

(b) analyzing she impedance characteristics for determining the presence of impedance transitions from one of the strata of the selected region to another;

(c) validating the presence of a host lithology in said strata based on said impedance transitions by determining whether said host lithology is substantially acoustically transparent, such that said impedance transitions from said strata primarily contain only survey noise; and

d) confirming the selected region possesses a host stratigraphy that is substantially acoustically transparent and is therefore a candidate for a subsequent seismic exploration for detection of the massive sulphide deposit.

3. The method of exploration according to claim 2, further comprising the steps of:

e) directing seismic waves at said host lithology and collecting reflected waves therefrom; and

f) analyzing the reflected waves for the presence of said massive sulphide deposit.

4. The method of exploration according to claim 2, wherein the step of validating the acoustic transparency of said host lithology further includes the step of checking for the absence of a recognizable peak in said impedance characteristics that exceeds the accumulation of the survey noise.

5. The method of exploration according to claim 4, wherein said impedance characteristics are represented by a vertical seismic profile.

6. The method of exploration according to claim 4, wherein said recognizable peak represents a seismic reflection from a geological boundary contained within said strata of said host lithology.

7. The method of exploration according to claim 6, wherein said seismic reflection is from the geological boundary other than a boundary of said massive sulphide deposit.

8. The method of exploration according to claim 2, wherein said impedance characteristics are determined from velocity and density measurements of the strata in said geological region.

9. The method of exploration according to claim 2, wherein the substantially acoustically transparent host lithology is represented by a seismic profile which contains a substantial absence of impedance markers of magnitude greater than that of any said survey noise contained in said impedance characteristics.

10. The method of exploration according to claim 4, wherein the substantially acoustically transparent host lithology is represented by a seismic profile which contains a substantial absence of impedance markers of magnitude greater than that of any said survey noise contained in said impedance characteristics.

11. The method of exploration according to claim 2, wherein the step of validating further includes a verification process selected from the group comprising bore hole data, numerical modeling, and multidimensional field surveys.

12. The method of exploration according to claim 2, wherein the survey noise includes geologic noise.

13. The method of exploration according to claim 2, wherein the survey noise includes ambient environmental noise.

14. The method of exploration of claim 2, where the survey noise includes instrument noise.

15. The method of exploration according to claim 2, wherein said host lithology is located above and below said massive sulphide deposit.

16. The method of exploration according to claim 15, wherein the step of obtaining said impedance characteristics is performed within a portion of a total depth investigation range of said strata of said geological region.

17. The method of exploration according to claim 15 further comprising the step of identifying a major marker in said impedance characteristics, the major marker adjacent to said host lithology.

18. The method of exploration according to claim 17, wherein the major marker represents a recognizable peak in said impedance characteristics while facilitating the determination of the acoustic transparency of the adjacent host lithology.

19. The method of exploration according to claim 17 further comprising the step of using the major marker to focus the search for said massive sulphide deposit.

20. The method of exploration according to claim 3, wherein the step of analyzing the reflected waves provides a seismic amplitude anomaly at least twice that of a contact within said host lithology, the seismic anomaly resulting from said massive sulphide deposit.