Table 10- 1 Overview of Typical Mechanical Core Orientation Tools at Home and Abroad
(A) the core side incision method
In this method, the spring carving knife installed in the core tube is used to draw lines on the side of the core as the basis of orientation. The SDQ series developed during the Eighth Five-Year Plan and the SDQ-94A directional coring device developed during the Tenth Five-Year Plan (Figure 10- 1) all belong to this type. It consists of two parts: an outer tube system for transmitting WOB and torque and an inner tube system for directional marking and coring. Three spring carving knives protruding from the inner wall of the inner pipe are installed in the inner pipe nipple, and the side notch of the core is directionally marked when the core enters the inner pipe. In general, the telescopic spring knife can get clear orientation marks, but when the cutting edge is worn or the core is too hard, the orientation marks on the surface of the core are not clear, or even can't be carved, so the spring knife is not easy to disassemble. When the core is too thin or eroded due to process or formation factors, it will also cause unclear notches and make directional coring fail.
Fig. 10- 1 SDQ-94A directional coring device
1-drill string; 2- reducing joint; 3- Upper outer tube; 4- centralizer; 5- spring; 6 direction keys; 7— Gravity accelerometer; 8-measuring instrument accommodating tube; 9— Directional joint; 10 axis; 1 1- sealing ring; 12- bearing; 13- water connection; 14- bearing; 15- adjusting nut; 16-directional screw; 17-core tube; 18-outer tube; 19-spring carving knife; 20— circlip seat; 21-circlip; 22— Drill bit
(2) Core end drilling method
In this method, a micro-drill is used to drill a hole in the end face of the core as a directional marker, and the marking and directional measurement are completed at the same time. YDX- 1 Core Orientation Instrument (Figure 10-2) developed during the Eighth Five-Year Plan period in China transmits the torque output by the turbine shaft to two diamond micro-drills, and pressurizes the micro-drills through the transmission box with a compression spring. Applicable aperture ≥ 91mm; The applicable hole depth is ≤200m, and the driving capacity of turbopump is ≥ 120L/min.
By this method, before the core is formed, the positioning mark is clear, and the positioning error will not be caused by the core fracture and distortion. The disadvantage is that the turbine at the bottom of the hole has complex structure, large volume and high cost. When the vibration generated by the turbine reaches a certain level, it is easy to cause the hole wall to collapse, which affects the marking effect and cannot meet the requirements of small diameter deep holes.
(3) Printing method
The printing core positioning device is shown in Figure 10-3. Before directional coring, grind the bottom of the hole with a special drill and wash it clean, and then run the offset printer into the hole with a drill pipe. The lower part of the printer is equipped with a cemented carbide indenter or colored pen in the same direction as the eccentric weight hammer. By using the self-weight of the drill pipe and the printer, punch marks (or color points) are left at the bottom of the hole or at the top of the unbroken core. The horizontal projection of the straight line between the perforation mark (or color point) located at the lowest position of the lower wall of the core and the center of the core is the azimuth line of drilling. Then lift the printer out, put the drill down, and grab the core marked with direction.
The advantage of printing method is that the orientation and printing mechanism are relatively simple, but the disadvantage is that the working reliability of eccentric heavy hammer is poor, and the orientation effect is not good when the drilling top angle is less than 5, so it can not be used for vertical holes, and it is difficult to obtain clear marks in hard rock strata.
The above three kinds of core orientation instruments are all used to calculate the occurrence of structural plane of rock and mineral seam from the bottom wall of borehole, and can be used when the borehole has a certain vertex angle. Due to some immature problems, this technology has not been widely used so far. In order to solve the problem of determining the occurrence of rock stratum by using single-hole core, it is necessary to study and improve the core orientation technology, improve its reliability and orientation accuracy, simplify the operation procedure and reduce the construction cost. The 3 13 geological team of Anhui Bureau of Geology and Mineral Resources cooperated with China Geo University (Beijing) to carry out the research on electric directional printing coring technology at the bottom of small and medium diameter drilling holes in deep prospecting, which overcame some shortcomings of traditional core orienter, made the core orientation mark clear and reliable, solved the technical problems of core orientation in straight and inclined hard rock layers, and expanded the application scope. The developed electric directional centralizer at the bottom of the hole won the national invention patent (patent number: ZL 20091KLOC-0/70005.8). The following focuses on the instrument and directional coring technology.
Fig. 10-2 YDX- 1 structure diagram of core guide
I- direction measuring instrument; Ⅱ-hole bottom power machine; Ⅲ-transmission working head
1-drill pipe; 2- upper nonmagnetic tube; 3- magnet block; 4— Upper inclinometer; 5— Put down the inclinometer; 6— Non-magnetic pipe joint; 7- Lower nonmagnetic tube; 8— Non-magnetic tube-power casing joint; 9— Upper bearing seat; 10-upper adjusting ring; 1 1- power machine shell; 12- stator; 13-rotor; 14-axis of rotation; 15-lower adjusting ring; 16- Lower bearing seat-; 17- chute coupling; 18-connecting pipe; 19-pressure spring; 20— Central axis; 2 1- gearbox; 22— transmission shaft; 23— Supporting pipe sleeve; 24— Marker bit
Fig. 10-3 schematic diagram of core orientation by printing method
1-drill pipe; 2- joint; 3- outer tube; 4- eccentric weight; 5— Indenter (or colored pen); 6-dent pit (or color point)