Conventional Drilling Method


The cable drill bit to the bottom of the well, driven by the power machine beam mechanism, so that the beam end up and down movement, and drive the wire rope and drill impact.Rock fragmentation, also known as percussion drilling (figure 1), is an ancient drilling method.The derrick of the cable drill has three pulleys, each passing through a wire rope, which are used to run the casing, bailer and hoist and lower the drill.Drilling with a cable drill must alternate with bailing.Due to its slow drilling speed and low efficiency, the rotary drilling has been gradually replaced by the rotary drilling.But it has the equipment simple, the cost is low, does not pollute the reservoir and so on the merit, may use in some shallow low pressure oil, the gas well, leakage well and so on.Therefore, in the United States and other countries there are still a certain number of oil and gas Wells with drilling method, China’s oil Wells in yanan region of northern shaanxi and sichuan ziliu area of salt Wells, the vast majority of drilling method is used to become.A rotary drill breaks rock by cutting or grinding the bit as it rotates.Is currently the most common drilling method (figure 2).First used in the United States in 1901.China began to use in the mid-1930s, it is faster than ton drilling, and can deal with well collapse, blowout and other complex circumstances, according to the power transmission mode, rotary table drilling and downhole power drilling two.The rotary table is equipped with a rotary table at the wellhead of the drilling platform. The rotating part of the rotary table has square holes. The kelly at the top of the drill string passes through the square hole, and the drill string and the drill bit are connected under the kelly.When the power machine drives the rotary table, it drives the drill string and the drill bit to rotate together, breaks the rock, the hole deepens along with the continuous extension of the drill string, and the cuttings return to the ground with the circulating mud.

Downhole power drill

Using the downhole power drill to drive the drill bit to break the rock.It is characterized by non-rotation of drill string during drilling, small wear and tear, long service life, especially suitable for drilling directional Wells.Underground power drilling has turbodrill, screw drill, electric drill, etc.The first two are driven by high-pressure mud and the second by electricity.In the early 1930s, the Soviet union first used turbodrill for drilling, while China began to use turbodrill and screw drill successively since the 1950s, mainly for drilling directional Wells.Electric drills require special wireline drill strings and have not been used in large quantities.

New drilling methods since the 1950s, some countries have studied new drilling methods, among which the laser method, the explosion method, the arc method, the electron beam method, the electric spark method and so on are all in the experimental research stage.
Blunt rotary drill
The percussion drill is connected to the drill bit, and the core of the percussion drill is pushed by circulating liquid or gas, so that the drill bit can break the rock by both percussion and rotation. Suitable for medium and hard formations.
Coiled-tubing drilling
Steel wire rubber structure of the flexible rod instead of the drill pipe, and connected with the downhole power drill, with a large diameter drum of the special ground equipment to lift down the flexible rod, can shorten the time of lifting down drilling, and can be in the lifting down drilling mud circulation. The industrial test well depth of the flexible rod drilling method has reached 2330m.
Erosion drill
High pressure (up to 1000kgf/cm2) is used to drive the well washing fluid with abrasive, so that when the well washing fluid passes through the wear-resisting nozzle of the drill bit, it reaches a high speed of 200m/s, and rocks are broken by erosion.

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