USING RECENT ADVANCES IN 2D SEISMIC TECHNOLOGY AND SURFACE GEOCHEMISTRY TO ECONOMICALLY REDEVELOP A SHALLOW SHELF CARBONATE RESERVOIR: VERNON FIELD, ISABELLA COUNTY, MI.

Wood, James R. ; Bornhorst, T.J. ; Chittick, S.D. ; Harrison, William B. ; Quinlan, W. ; Taylor, E.

Michigan Technological University

关键词: Leaching;    Hydrocarbons;    Iodine;    Enzymes;    Economics;   

DOI  :  10.2172/816081
RP-ID  :  NONE
RP-ID  :  FC26-00BC15122
RP-ID  :  816081

美国|英语

来源: UNT Digital Library

【 摘 要 】

A principal goal of the Budget Period I was to demonstrate that surface geochemistry could be used to locate bypassed hydrocarbons in old fields. This part of the program was successful. A surface geochemical survey, employing 5 different techniques, was carried out in the Spring and Summer of 2000 and a demonstration well, the State Vernon & Smock 13-23 HD1 (permit number: PN 53945) was drilled in Vernon Township, Isabella County, Michigan in the late fall of 2000. A demonstration well was selected and drilled based on geologic considerations and surface geochemistry. Over 460 soil samples were collected and analyzed over the drill site. A good anomaly was detected near the proposed well site and the demonstration well, the Smock 13-23, was drilled to a depth of 3157 feet by November 17, 2000. Two laterals were drilled, and hydrocarbons were located in a zone approximately 175 feet in length. However, it was determined that the pay zone was too small and difficult reservoir conditions (water production) prevented putting the well in production. The Smock 13-23 was shut in and abandoned January 15, 2001. A post-mortem determined that the main reason the well was not economic was because the zone was nearly completely flushed by earlier recovery operations. The post mortem also revealed the presence of an unmapped shale plug crossing the first lateral. It appears that this shale was detected by the geochemical survey, but its significance was not appreciated at the time. It is possible that sections of the well were faulty, ''porposing'' up and down so as to create water blockages. We are continuing to use the Vernon Field and the demonstration well to calibrate the geochemical data. Eventually, this study may provide a standard site that can be used to test and calibrate geochemical anomalies, something that does not presently exist. A postmortem report on the well, including the geology and geochemistry used to site the well, is presented in Appendix I. Five geochemical techniques have been tested in Phase I. These include surface iodine, microbial, enzyme leaching, soil gas and subsurface iodine. We are most comfortable with the results of the microbial surveys but feel that direct measurement of soil gas is the best method if analytical difficulties can be overcome. The reason the microbial surveys are presently favored is because they provide a logical, consistent picture that is easy to interpret and easy to explain. This in turn is because the microbial anomaly is manifested as an ''apical'' as opposed to an ''edge'' or ''halo'' anomaly. Several lessons were learned during Phase I activities. The main one was that surface geochemistry could locate anomalies over old fields such as Vernon. We also learned that horizontal drilling has advantages and disadvantages in situations such as this. On the plus side, it does provide a means to probe for pockets of bypassed oil, but it is expensive relative to vertical (or slant wells?) and is difficult to control in a narrow pay zone. We tentatively conclude that horizontal wells do not provide a cost-effective solution in this setting and suggest that geochemical anomalies be investigated via a single vertical well or multiple vertical wells.