V. DRILLING OPERATIONS AND PROJECT MANAGEMENT

In the sub-Sections below, we first provide additional operational details for the phases of the project associated with rotary drilling and continuous coring. This includes the "rig-related" activities associated with downhole measurements of pore pressure, permeability and stress through perforations, as described previously in this proposal. We then discuss the plan for on-site technical personnel, summarize the services requested from ICDP (to whom this proposal is also being submitted) and outline our strategy for project management.

 

Rotary Drilling

Figure 20
Figure 20. Direction drilling program for the Parkfield hole. (click for more information)
A detailed drilling and operational plan has been prepared for this project by Mr. Louis Capuano, President and co-founder of ThermaSource, Inc., a geothermal engineering consulting company. Mr. Capuano has almost 30 years of experience in both oil and gas and geothermal drilling and serves on a number of drilling advisory panels. In this Section, we summarize the plan he developed through extensive discussions with Mark Zoback and Steve Hickman utilizing a preliminary drilling plan developed by ICDP as a starting point. The information provided in this Section and in Appendix A is intended to provide the reader with more detailed information about the drilling, coring and operational plans than is described above. This information is excerpted from a highly detailed report entitled "San Andreas Fault Zone Drilling Project: Drilling Program and Cost Estimates" (henceforth termed Drilling Report), that was prepared by Mr. Capuano. Copies of this comprehensive report will be provided to NSF under separate cover. While Section VI provides summary budgets for operational aspects of this project (as well as science), the detailed budget breakdowns for the many individual aspects of the operations, services, supplies, etc., associated with drilling are provided in the Drilling Report.

Figure 20 shows a detail of the planned trajectory for the rotary hole in both cross-sectional and plan views. Together with the geologic and geophysical criteria summarized in Section III, a number of practical and engineering considerations were used in designing this directional drilling plan:

Figure 21
Figure 21. Drilling and casing program for the proposed Parkfield hole. (click for more information)
The hole sizes (drill bits) and casing diameters shown in Figure 21 were similarly designed on multiple criteria:

A breakdown of the time required to drill this hole and conduct rig-related downhole measurements (210 days total) is shown in Figure 22 and described in a step-by-step manner in Appendix A. In preparing this timeline, reasonable and conservative assumptions were made about the rate of penetration. As is also described in Appendix A, should drilling problems necessitate use of the contingency plan, the resultant hole will be smaller (6 1/8" open hole with a 5" casing). This will still allow coring of the multilaterals, downhole measurements and monitoring instruments to be used, albeit with somewhat less flexibility. Interestingly, the total time required to drill the contingency hole is also estimated to be about 210 days, which results in negligible changes in the overall cost of the rotary drilling phase of the project, as described in the Drilling Report.

 

Testing Through Perforations

Figure 22
Figure 22. Depth versus time curve for the Parkfield hole. (click for more information)
The procedures associated with the fluid sampling and pore pressure, permeability and least principal stress (i.e., hydrofrac) measurements through perforations are somewhat complicated. These measurements require the cemented casing to be perforated at 10 different depths, packers to be used to isolate the test zone from the rest of the hole, and all of the test intervals to be re-cemented prior to the fault zone monitoring phase of the experiment. To minimize the rig time and costs associated with this part of the project, a number of experimental procedures were investigated. The procedure decided upon is termed a "Squeeze Retainer Procedure" and permits the tests to be conducted in sequence (see Drilling Report). This procedure involves the following steps, working from the deepest test interval upward:

  1. Perforate the test zone with a wireline casing gun.
  2. Run in with a composite packer on the drill string and set it above the perforations.
  3. Conduct a drill stem test (DST) to estimate formation permeability and pore pressure from pressure build-up; use a wireline sampler inside the drill pipe to obtain fluid samples (26 hours).
  4. Conduct hydraulic fracturing test with multiple pumping cycles to determine the least principal stress (6 hours).
  5. Pull drill pipe out of the packer; displace almost all of the fluid out of the pipe with cement.
  6. Stab pipe back into packer and squeeze cement below packer into perforations.
  7. Pull drill pipe out of packer and wait for cement to cure.
  8. Perforate next test zone with wireline casing gun.

As explained in Appendix A, there is a prescribed sequence of operational steps to make this possible. It is estimated to take approximately 61 hours to conduct each measurement; the next test interval will then be perforated and the entire procedure repeated. When these tests are complete, the composite packers left in the hole and residual cement inside casing will be drilled out to leave the borehole with all the perforations plugged. Pressure testing will be done to assure that this is the case. Any leakage from perforations will be re-cemented ("squeezed"). This entire downhole measurement program will take about 3 weeks of rig time to complete and should yield a comprehensive suite of fluid samples and pore pressure, permeability and least principal stress measurements at varied depths and positions within and adjacent to the fault zone. At the end of this sequence of measurements, a single interval will be perforated in order to monitor fluid pressure during the initial fault zone monitoring phase of the experiment. The drill rig will then be demobilized.

 

Continuous Coring

Figure 23
Figure 23. Case history for multilateral, directionaly drilled hole in Prudhoe Bay, Alaska. (click for more information)
Once we know where coring will provide the most useful information about the fault zone (from a combination of geological, geophysical and seismic observations), the series of multilateral core holes described above will be drilled. The specifications cited in the "case history" described in Figure 23 (from an advertisement for one of the service companies that do this kind of work) are, in fact, fairly similar to those in this project. The depth at which the multilaterals (~4 km) is similar and the diameter of the main borehole (7") is the same. The length of the drilled sections (~500 m) is somewhat longer than the lengths we wish to core (250m). As in our project, a slotted liner (a porous, uncemented casing) was left in each multilateral hole. The purpose for utilizing the case history in Figure 23 is obviously not to endorse a particular service company. Rather, we present Figure 23 to emphasize the fact that the technologies required to carry out this phase of the proposed project are currently in use by the petroleum industry.

As described in Appendix A, we propose to bring in a separate rig for the coring phase of the project. The budget (Section VI) is based on the assumption of bringing in a deep wireline coring rig. If possible, we would like to use the DOSECC deep coring system that is being used for the first time in the Long Valley drilling project at the time this proposal is being written. As the ultimate capabilities of this system are not known at this time, we have not based the coring plan on using this system. However, if it can be used for this project, we will want to do so.

We estimate that it will take 53 days to obtain the desired core (see time breakdown in Appendix A). The procedures for core handling are described in the previous Section. Our current plan is to leave each core hole open (with a slotted liner in it) to enable pore pressure to be monitored at multiple sites in the fault zone.

 

On-Site Technical Personnel

The detailed drilling plan and budget submitted under separate cover lists a number of cost items associated with personnel. While budgets are presented and discussed in Section VI, there are several points to note here because of their overall affect on operations. First, the budgets include all supervisory personnel associated with drilling. Thus, in addition to the personnel provided by the drilling contractor(s), there will be drilling personnel on site 24 hours/day representing the project science team who will be providing supervision of drilling operations, keeping track of progress and expenditures and working with the scientific project management team (see below) to assure that the goals of the project are met, on time and on budget.

As this project requires extensive efforts related to real-time sampling of cuttings and gases, the drilling budget calls for an additional geologist to be provided by the mud logging contractor. This means that there will be 2 people on site 24 hours/day to assure that sampling and sampling equipment are functioning properly. Special equipment, such as the gas collection/gas chromatograph/mass spectrometer system being provided by PI Jörg Erzinger requires special manpower and attention.

Finally, we have budgeted for 2 geologists/technicians to be on site a total 135 days during the rotary drilling phase of the project and the full 50 days associated with coring. These individuals will be able to assist the science team with the innumerable on site technical activities, including:

Operations at Long Valley indicate that a 3 person staff is needed on a 24 hour basis to keep up with continuing coring operations. As a member from the PI team will be on site continuously, the 2 positions budgeted here will assure that adequate personnel will be on site to handle incoming core. As described in the Drilling Report, the drilling plan includes costs for trailers to provide onsite office space and housing for both supervisory and on site scientific personnel.

 

Services Requested from ICDP

This proposal is being submitted to the International Continental Drilling Program as well as the National Science Foundation, the U.S. Geological Survey and the U.S. Department of Energy. The ICDP can provide invaluable assistance in a number of areas:

As mentioned above, we have budgeted for onsite technical personnel to interface with the ICDP data base systems. They will need training and periodic supervision by ICDP personnel.

 

Project Management

The management team of this project consists of Mark Zoback, Steve Hickman and Bill Ellsworth. Working together, these three individuals have hosted numerous planning meetings and workshops, represented this project at even more numerous national and international scientific meetings and special symposia, and worked closely together to develop this proposal. The responsibility for overall project management and interfacing between the scientific and operational personnel will be shared by Mark Zoback and Steve Hickman.

As representatives of the different science teams, these three individuals will continue to coordinate the various groups of scientists as follows:

Steps to be taken to assure optimal project management are as follows:

As Zoback, Hickman and Ellsworth have been friends and colleagues for ~20 years (and Zoback and Hickman have worked together on many other drilling and downhole measurement projects over the years), we feel that the shared management approach described here will be successful.

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