Dr. TONKING. My name is William H. Tonking, and I am the deputy project manager for Brown & Root, Project Mohole. Mr. Chairman and members of the committee, it is a pleasure to be here today to review and summarize the research and design work accomplished to date; to present the overall requirements and criteria; and to define the engineering plan that at this time appears to offer the best assurance of accomplishing the scientific objectives of the project. The prime contractor is well aware of the ramifications of the national scope of the project and is most cognizant of the funding situation. In the conduct of the project, every effort has been made to be objective in engineering studies, costs, and time estimates. Proper expenditure of Government funds is a foremost consideration by the entire staff and attempts have been made by all to reduce expenditures wherever possible and feasible without influencing the quality and progress of the task at hand. In general, the program consists of several systems. Some are composed of items readily available, some require but slight modifications, and others involve new, unusual, and time-consuming developments. The engineering studies and data contained herein are presented as a means to an end; namely, the accomplishment of the scientific objectives of the project. The major scientific objective of Project Mohole is to obtain a core record of the layers of the earth's crust and the upper part of the underlying mantle. In addition to the core samples, important information will be acquired from various measurements made in the hole both during and after completion of drilling. It is well understood that scientific data collected and recorded during the term of the project must be of the highest quality and in amounts that will enable reliable and realistic interpretation. The lessons imparted from the operations of phase 1, the Guadelupe drilling, have been carefully and thoughtfully considered in the research and development required for the project. The results from phase 1 have been utilized wherever applicable in the present program. This paper shows in brief the work to date; and, it must be understood that continued improvements and refinements will be accomplished in arriving at the best solutions to the many problems of drilling the Mohole. The final and acceptable solution will be the one used in performing the ultimate task. Improvements and advances in technology will be incorporated into the project as they are developed. The valuable advice and suggestions of the National Science Foundation and Amsoc Committee of the National Academy of Sciences have been most informative in constructing this plan. A continued cooperative effort will assure the best possible return on the investment with the least possible risk. PROGRESS AND PLAN SITE SELECTION The first consideration is the selection of the drilling site. This selection requires that thickness, structural attitude, and composition of the unconsolidated sediments and other crustal rocks be defined as completely as possible and that movements of air and water be measured over as long a timespan as possible. Because serpentinite dredges had been recovered from the north wall of the Puerto Rico outer ridge, a 1,000-foot core hole was drilled in serpentinite on land near Mayaguez, Puerto Rico as a possible aid to site selection in this area. Physical, chemical, and mineralogical properties of these cores are now being determined by specialists. Seismic exploration of sites I and II was completed in March of this year and interpretation of these data is 95 percent complete. At Puerto Rico outer ridge (site I), 240 miles of reflection profile and 160 miles of reversed refraction profile were obtained. At site II (Barracuda Fault), the data included over 100 miles of reflection. profile and 60 miles of reversed refraction profile. Some oceanographic data were also obtained by the seismic crew. These included water current data from drogue trackings, wind velocity from a recording wind vane, and wave heights and velocity from a recording accelerometer. The outer ridge was found to be structurally complex in that the area is intensely faulted. Actually, the faulting extends into the mantle. This is the first time that any definitive proof has been brought forward that faulting in the oceanic crust does extend into the mantle. Because of the intensity of the faulting, the determinations of the depth to Moho are not too exact. The extent of the fault blocks, in many cases, is less than the distance between the shooting ship and recording ship necessary to obtain refractions from the mantle. Nevertheless, because of the instrumentation and techniques employed in this survey, these depth determinations are the most exact that have been calculated for the outer ridge though still probably only accurate within plus or minus a kilometer. A zone 1,500 to 2,000 feet thick that is seismically transparent has been noted on the outer ridge. The accoustical velocity of this zone varies little from the velocity of sea water. These materials must be classified as mush and, thus, would have little, if any bearing strength. You gentlemen can realize the extreme difficulty of installing any heavy equipment on this type bottom in 18,000 feet of water. The Barracuda Fault area, approximately 150 miles east of Antigua is structurally less complex than the outer ridge. Here, a hole could be located immediately upon the upthrown block where no bottom sediments exist. However, sedimentary deposits have accumulated downdip on the upthrown block to the southwest. Although there is still some interpretation of these refraction data to be finished this area looks quite promising. We may very well have to take another seismic look at it when we complete the evaluation and interpretation of our shooting in Hawaii. Seismic surveys were initiated on the Hawaiian arch September 29, 1963. The first area shot was only about 15 miles north of the Island of Maui where Dr. George Shor of Scripps Institute had found an anomalous area. We substantiated his findings and found that the area is atypical because essentially the third crustal layer is missing. At present, the crews are shooting in approximately 13,000 feet of water on the Hawaiian shelf about 150 miles north of Maui. Preliminary interpretation indicates that the crustal structure is much simpler than at the Atlantic sites. Data are excellent and the depth computations will be more reliable and accurate than those from the Atlantic work. The same oceanographic measurements are being made here as were made in the Atlantic. In addition, punch cores will be obtained from materials of the ocean bottom. The reflection and refraction shooting is under the direction of a staff geophysicist in collaboration with a geophysicist of the National Science Foundation. Also of interest is the benefit that other governmental agencies have received from our shallow shooting off Maui. The USGS set up seismograph arrays on two different islands to record our shots and apparently received very good signals. Upon completion of the interpretation of all proposed sites, we plan to critically review all data with the Amsoc and select an ocean by March 1, 1964. It is anticipated that additional seismic work then may be necessary to pinpoint the actual Mohole site. The final interpretation of all these data will not only provide information for site selection but will make significant contributions to the understanding of deep ocean geology. SUMMARY OF SCIENTIFIC INSTRUMENTATION The down-hole instrumentation program has been developed around the fact that the major objective of the project is to obtain all pertinent scientific data about the earth's crust and upper part of the mantle. A study of the Amsoc recommendations of December 1962 and a study of the general scientific objectives were made to determine the extent and type of measurements required. The required measurements fall into four broad classifications: geological, geophysical, drilling, and auxiliary logging. The measurements in the first two classifications include the prime objective of the project. The second two classifications provide the necessary information to obtain these measurements with a high degree of reliability. The geological classification includes the complete coring program aboard the drilling vessel as well as the necessary down-hole instruments for obtaining oriented cores. The geophysical classification includes the in situ measurements necessary for correlation as well as the basic electric, magnetic, and physical rock properties. Also included in this classification are measurements of the earth's magnetic field and the propagation phenomenon of magnetotelluric currents. The drilling classification includes the measurements of hole diameter, inclination, and the direction of inclination. The auxiliary logging classification includes measurements for logging-cable tension, cable speed, cable depth and a constant-tension device. Also the down-hole strain gage and swivel head instruments are included. A general logging program has been initiated to obtain these measurements. This program resulted from a study of the existing logging techniques, the general objectives of the down-hole measurements and the tentative drilling program. In general the down-hole environment in which the logging instruments must operate are the following: Within a 6-inch diameter, on the end of 40,000 feet of seven-conductor logging cable, in a relatively corrosive drilling fluid with a density between 8 and 10 pounds per gallon and an electrical resistivity of 0.1 to 0.5 ohmmeters, and a maximum ambient temperature of a relatively high value. With one exception all of the environmental conditions are either known at this time or will be known at the time of final instrumentation design. The one exception is temperature. A study was made of the existing data on measurements of heat flow, thermal conductivity and temperature gradients in the Atlantic and Pacific oceans. The conclusions that were reached are that 200° C. is a very reasonable assumption for the maximum temperature to be encountered at Mohole depths. It also indicates that this is a statistical value and it is possible for maximum temperatures to be above as well as below this value. From these conclusions and from the fact that this temperature is presently the maximum operating temperature limit for practically all electronic components this value has been chosen as the design specification. With respect to the logging program a survey was made of the instruments and equipment presently available in the well logging industry and the electronic instrumentation industry. From this surrey it was apparent that the instruments necessary for the Mohole program fall into three classes: Instruments that are presently available, instruments that are presently available but will need modification, and instruments that will have to be completely designed and developed. In addition to obtaining instruments necessary for measurements specifically asked for by the Scientific Objectives and Measurements Panel of the Amsoc Committee, work has been directed to determine if other techniques and measurements could be added which would provide additional useful scientific data. The status of the scientific measurements and logging program can be summarized as follows. The three instruments considered basic to the program are acoustic velocity, gamma-gamma (density), and oriented sidewall coring. Major development is required on magnetic field intensity, magnetic susceptibility, high resistivity, core orientation, rock strain, and thermal conductivity measurements. The rest of the instruments being considered for the program will require various degrees of modification. All will be required to operate on 40,000 feet of conductor cable. The basic components required for the surface handling of the downhole instruments are presently being designed in detail. These include the winch drum, winch drive, logging cable, cable-wear indicator, cable-corrosion inhibitor, and vessel-heave cable compensator. For the core orientation instruments, detailed tests are being conducted to determine the necessary modifications of a present hard rock sidewall coring tool for Mohole use. Several systems have been studied to obtain the orientation of this device while coring and both magnetic and inertial systems have been given consideration. The inertial reference system has been selected to permit periodic calibration of magnetic survey instruments. At the present time, the basic gyro systems are being designed. Because of the fact that the maximum anticipated temperature is not known with certainty and that there exists a possibility that it might exceed the design maximum, continuous extrapolation of maximum temperature will be made as drilling progresses. This program includes preliminary heat flow measurements at the selected site and continuous periodic thermal conductivity measurements on the cores obtained while drilling. When and if sufficient data have been collected to indicate with some degree of certainty that the bottom-hole temperature will exceed the specified maximum, a program will be initiated further to upgrade the measuring instruments. The following techniques may be employed if bottom-hole temperature exceeds that for which the tool was originally designed: 1. Drilling-fluid-circulation cooling. 2. Localized cooling of critical components outlined in the Peltier phenomenon. 3. Encapsulating critical components or modules of the instrument in Dewar flasks. 4. Using the heat of fusion technique with a double wall instrument house containing some metallic salts. 5. A complete redesign of electronic circuits and components to operate at the higher ambient temperatures. After the hole has been drilled, it is desired to place a permanent monitor package in the hole which should be capable of transmitting information to the surface for a period of at least 1 year. Four basic measurements are contemplated: magnetotelluric currents, temperature, seismic information, and rock strain. Investigations of the necessary instrumentation and the required sensitivities of these instruments for use in this bottom-hole monitor have been made. Further detailed investigations of the seismometer measurements and magnetotelluric measurements are in progress. In keeping with the general objectives of the program, core measurements are being given prime consideration. Using the recommendations from the Amsoc Committee report of December 1962 as constituting the minimum specifications, a core measuring program and a study of necessary facilities have been made. On-vessel measurements of the cores will provide magnetic, electrical, radiation, density, acoustic and other physical, chemical, and biological properties necessary to obtain the maximum scientific information from the cores. Detailed scientific measurements will be made in scientific laboratories by specialists. DRILLING A drilling system has been designed that utilizes proven equipment design principles and materials, and standard engineering practices to the fullest extent. DERRICK AND SUBSTRUCTURE The derrick will be rated for a 2 million pound maximum hook load. The derrick will also be capable of resisting rotating equipment loads and loads imposed by wind and vessel motions. The derrick is designed to be a sectional welded type, 147 feet high with a tracking system for the traveling block and rotating equipment. Two derrickman elevators will be provided for access to traveling equipment and the crown block. A rotating beacon and radar antenna will be installed above the crown block. The overall height from the platform deck to the top of the radar antenna will be about 200 feet. The substructure will be capable of withstanding loads imposed by the derrick, the drawworks, drilling tools, pipe standing in the derrick, the drill string suspended at the rotary table and dynamic forces due to vessel motions. A spider deck will be provided below the lowest plat |