In oil production process, almost all of the reservoir will be affected by different degree of damage in the maintenance process from exploration to development and later in the. In the existing reservoir protection technology, mostly well killing fluid or shaft working fluid from the aspects of optimization to minimize the formation damage. For the realization of reservoir protection in real sense, the introduction of Snubbing operation technology in recent years.
A brief, Snubbing operation technology
1 the concept and significance
Snubbing operation technology is a kind of operation method in pressure environment by professional and technical personnel to operate special equipment lower pipe column. At home and abroad has been widely applied in underbalanced drilling, sidetracking, slim hole drilling, completion, perforation, oil test, test, acidizing, fracturing and workover operations.
Application of Snubbing operation technology has the following meaning.
(1) the maximum keep the original formation condition of oil and gas reservoirs, the correct evaluation of oil and gas reservoir. Well killing fluid into the formation, resulting in the formation of pollution, has brought the negative influence for the follow-up data recording, completion, oil test link, which affects the reservoir description result, until the impact to recovery. By working with pressure technology can make the physical production layer can be protected to the maximum extent, to avoid the production of the new layer of mining damage caused by conventional mining process, such as the new production of oil and gas pore clogging, mud cake phenomenon caused by stratigraphic interpretation errors, water sensitive mineral swelling caused by a decline in production of reservoir property, thereby to obtain the accurate data in reservoir evaluation.
(2) minimizing the operation risk. Well killing fluid in operation in the process of gas or oil penetration, lower density, dangerous hand blowout of large, on the other hand, the need to repeat the pressure well, the process is complex, expensive.
(3) to solve some difficult problems of conventional pressure wells. Such as gas well operation, kill manifold fracturing hydraulic well, often a pressure on the leak, do not pressure spray, low permeability gas wells is easily crushed. And due to the application of pressure operation technology, to avoid the frequent use of high pressure oil well - flushing fluid replacement, circulation and facilities on the ground, to avoid environmental pollution, and the problem can be solved in water injection well long time discharge overflow.
(4) avoid the use of killing fluid production layer, prevent from pollution, so as to improve the productivity and recovery, so that the production of layer production yield and potential is the greatest protection.
(5) reduce the exploration cost, improve the oil and gas field production efficiency and economic benefit. As the need for well killing job, one is to save the cost, shorten the operation period is two. The pressure and the harm to the strata is self-evident, well killing fluid charges are also very impressive, and after the operation still need pumping well killing fluid. But the well operation, stopping water injection pressure release time is long, sometimes even two or three months or half a year, in order to maintain formation pressure field balance, surrounding wells also need to stop injection, reduce oil production or stop production, a greater impact on production, economic benefits is low.
(6) to protect the environment, to avoid killing fluid on the surface of the pollution and meet the requirements of HSE, which has great social benefit.
2 foreign application status
In 1929, Herbert C.Otis proposed the idea of Snubbing operation, and the use of a static and a dynamic double reverse slip group supporting tubing, achieved through the wire rope and winch control oil pipe lifting. In 1960, Cicero C.Brown invented the Snubbing operation device for oil hydraulic lifting, thereby, the Snubbing operation machine can become a complete system independent of drilling or workover rig. In 1981 VC Controlled Pressure Services LTD. to design the vehicle hydraulic Snubbing operation machine, this innovation makes the Snubbing operation aircraft with high maneuverability.
In 40 years, hydraulic Snubbing operation machine is a great deal of improvement and development, expanding the scope of application. At present, the hydraulic Snubbing operation machine operating speed, efficiency, adaptability and efficiency and its application in the oil field proven, hydraulic Snubbing operation machine is no longer simply for "disaster service", and gradually became the important production tools, and can be used effectively for the desert, jungle and large-scale workover rig is difficult to travel congested city.
At present, snubbing equipment development in foreign countries have been relatively mature, full hydraulic Snubbing operation machine dominated. According to statistics, foreign manufacturing Snubbing operation, snubbing technology services or both manufacturing and service companies to provide more than 10 job. Snubbing equipment used in terrestrial and marine equipment to achieve the full hydraulic lift, slips and BOP actuating mechanism to realize the hydraulic controlled remote control; enhance the highest up to 2669kN, maximum thrust of 1 157kN; trip to about 3M based, the maximum operating pressure of up to 140MPa and.
3 domestic situation
China's twentieth Century 60 time had developed wire rope type snubbing device, it uses conventional tractor hoist winch lower pipe column, on the well self sealing device of sealing oil casing annulus. This device has the advantages of simple structure, convenient manufacture, easy to master, but has the disadvantages of complicated operating procedures, large labor intensity, poor safety performance.
At the end of the 70's developed a skid mounted hydraulic Snubbing operation device, can be used for 4MPa workover wellhead pressure. Despite the development experience and work better, because at that time the understanding of Snubbing operation deficiency, and the manufacturing level of hydraulic components is low reason, has not been popularized.
In 80's in China has developed vehicle hydraulic snubbing workover rig, currently available for the wellhead pressure is higher than that of 15MPa snubbing operation.
The application field of 4 Snubbing operation machine
Snubbing operation machine is mainly used for water injection wells and flowing wells and gas wells and routine work under a fixed tube column layer fracturing and acidizing and completion operation. Its main application areas are the following.
(1) for high production wells, key wells in oil and gas field. The characteristics of these wells is big contradiction of high yield, high formation pressure and also between layers, these well application Snubbing operation machine for workover without high pressure hydraulic well well, so as to reduce the damage to the formation, reducing the effect of interlayer contradiction, shorten the production period of recovery, improve the output of crude oil.
(2) used for water injection well. Snubbing operation machine is not overflow, blowout, put no pressure relief case pressure tubing. Can solve the problem of sewage emission, lower the cost of treatment, reduce the time of operation for well, improve the production efficiency of water injection wells, to prevent local formation pressure loss.
(3) used for underbalanced drilling. Can realize the formation pressure is higher than the safe drilling fluid column pressure, is conducive to the protection of low pressure reservoir, for oil and gas exploration wells in favor of discovery.
(4) achieved without pressure under the condition of layered fracturing wells. Using the matching pipe string, Snubbing operation machine in a pressure situation, layer by layer on stratified fracturing pipe string implementation of layered fracturing, avoid the use of well killing fluid, not only avoid reservoir pollution, but also to speed up the construction schedule.
(5) achieve underbalanced perforation. Can achieve the purpose of increasing yield of induced flow, especially in the light of the key wells drilling, can more truly reflect the formation conditions.
(6) for the completion of fishing, milling and other workover operation pressure. Because the Snubbing operation machine with rotary table can be completed its own facilities, fishing, milling and other workover operation pressure.
To sum up, because the Snubbing operation technology has its unique advantages, but also in foreign countries is as a mature technology in the widely used, so according to the present situation of domestic oil and gas fields, the technology as a reservoir protection and environmental protection of new technologies, new technology has the broad application space.
Generally speaking, Snubbing operation is a challenge to the conventional well pressure operation mode, compared with the conventional mode of operation, Snubbing operation has the incomparable superiority. No matter from the resources sustainable utilization, rational mining, improve the recovery rate, or from the economic and social benefits, both for oil and gas of long-term development, stable production and ground environment provides strong technical support.
Two, the Snubbing operation machine
Snubbing operation machine is refers to the pressure in the wellbore conditions for snubbing, an advanced implementation of measures to increase the operating equipment. In the United States, Canada and other countries, the popularization and application of the equipment rate of 90% or more, are operating in snubbing conditions, greatly reducing the production time, improve production efficiency. Especially in North America and the Middle East oil and gas producing areas of major, this equipment has brought the enormous economic benefits and social benefits for the oil company.
According to the different operating conditions and equipment investment, there are mainly three kinds of Snubbing operation machine.
1 independent work Snubbing operation machine
Independent work Snubbing operation system without the workover auxiliary operation is an operation machine with high efficiency and safe, economy. Sealing device independent from under the tubing through elastic in confined conditions, does not need the derrick or operating machine matching, can independently finish the job service. By the general Snubbing operation, the wellhead workover dedicated carrier truck, pump truck, crane, with trailer acquisition vehicle and equipped with AC generator duty car etc..
(1) snubbing wellhead device is shown in figure 1. The wellhead device is connected to the development of independent system, is convenient for quick installation and integral hoisting transportation in the truck platform.

Figure 1 Snubbing operation wellhead independent operation device
Activity 1 slips, 2 fixed slip, 3 tubing from the liquid cylinder, 4 annular BOP, 5 balance discharging ballast, 6 rapid replacement of BOP, 7 full sealing blowout preventer
(2) procedures. Fixing device installed first around the wellhead, snubbing device to ensure safety; and then install type blowout preventer, snubbing device is arranged in the blowout preventer and composed of a fixing device and reliable fixation; 196.1kN acquisition vehicle with a cable winch 22m mast, used to assist the tubing at the by the pump; pressurized to 21MPa for snubbing device and BOP system pressure test. The complete set of equipment arrived at the scene within 1 ~ 1.5h can be assembled and work. The system can be put into 1 tube wells in snubbing case average lmin, security, fast 3500m downhole operation and other drilling, well completion, workover, well cementing, fracturing, salvage, windows, side drilling equipment is fully compatible with.
2 and the derrick (or drill) with unit machine using Snubbing
And with the main equipment of Snubbing derrick unit machine uses is a special hydraulic device, in conjunction with derrick and other downhole operation tool (hydraulic tongs, wire rope and tools), composed of a tubing from under the hydraulic cylinders and hydraulic blowout preventer device, to complete a variety of workover and pressure operation with drilling the field operation personnel, and ensure safety.
(1) the composition. The homework machine system consists of power source, hydraulic system, oil pipe up the liquid cylinder, hydraulic tongs, hydraulic clamp, hydraulic blowout preventer, accumulator and the nitrogen tank, the upper and lower working platform and ladder, escape device, pump and tank, duty room, tubing flat car, etc..
Wellhead device for independent system connected into a whole, can be installed and put people to work quickly, and can transport in integral hoisting truck platform.
(2) procedures. Prepare a first oil pipe pressure people close the upper annular BOP balance upper pressure opened lower part of a mounting tubing hanger a closed annular BOP equilibrium pressure at the bottom of upper opened a tubing hanger export a slow release of Snubbing operation machine pressure BOP BOP, ensure wellhead blowout preventer no leakage opened the Snubbing operation machine in 3 blowout preventer to remove suspended pipe column device on a Snubbing operation machine to uninstall installed wellhead.
3 and the hydraulic workover rig with unit machine using Snubbing
With the hydraulic workover rig with the use of Snubbing operation. The matched electric hydraulic workover rig, can perform any conventional drilling and workover tasks, with automatic connection, open the oil pipe device. In the shut in pressure situations can play under the tubing or drill pipe work. SJ400 electric hydraulic working machine bearing 1779.3kN, equipped with 279.4mm (11in), 68.9MPa BOP, can be used as a conventional drilling, underbalanced drilling, sidetracking in directional drilling, milling and other operations.
Snubbing operation machine faults: one-time investment is huge, site installation, workload is big, complex technology.
The technical index of Snubbing operation machine at home and abroad:
The maximum bearing pressure of foreign oil of Snubbing operation 140MPa; 2669kN maximum lifting force; maximum thrust under 1157kN; hydraulic cylinder distance of about 3m. The highest pressure for domestic oilfield Snubbing well unit is 35MPa; the highest lifting force is 658kN; 431kN maximum thrust, liquid cylinder around 3m.
In three, operation device with pressure
Operation device with pressure used at home and abroad are mainly three categories: low, medium, high pressure.
1 low pressure operation device with pressure
Low voltage operation device with pressure as shown in Figure 2, there are three main types of tubing and collar, in the rubber seal conditions, forced through the sealant, when gravity is greater than the downhole tubing downhole pressure of oil pipe jacking force, available operation vehicle hook up tubing, downhole tubing downhole pressure when gravity is less than the oil pipe jacking force, the application of fixed propping prevention kava and travelling propping prevention kava and a lifting oil cylinder is derived and the coupling pipe. Tubing seal using self head and hydraulic cylinder shaped rubber core annular BOP; by increasing short and ram BOP export tool. Dynamic sealing pressure of not more than 7MPa. The whole operation process by operating vehicle with the completion and operation device with pressure.

Figure 2 low pressure operation device with pressure
1 walk slips, 2 cross member assembly, 3 double stage cylinder, 4 overflow nipple, 5 level adjustment assembly, 6 fixed slip, 7 cylindrical BOP, 8 beam assembly, 9 safety slips, 10 double ram blowout preventer wellhead, 11 four, 12 transverse beams assembly, 13.5 1/2in production casing.
2 medium pressure operation device with pressure
Medium pressure operation device with pressure as shown in Figure 3, the dynamic seal pressure is not more than 14MPa, the static seal pressure is not more than 21MPa, tubing seal in plastic conditions under the collar up, through the upper and lower two fast ram BOP derived, plastic damage is light, long service life, operation device with pressure and working vehicle with the completion of the tubing under.

Figure 3 medium voltage operation device with pressure
1 beam assembly, 2 swimming slips, 3 fixed slip, 4 beam assembly, 5 upper annular BOP elevation, 6 short, 7 annular BOP, 8 cross member assembly, 9 three ram blowout preventer wellhead four, 10, 11 on the cross member assembly, 12 lift cylinder, 13 swimming slips, 14 level adjustment assembly, a 15 cylindrical BOP, 16.Fzl8-35 ram BOP, 17 fixed slip, 18 cross member assembly, 19.FHl8-35 annular BOP, 20 three ram blowout preventer wellhead four, 21, 22 cross member assembly.
3 high pressure operation device with pressure
High pressure operation device with pressure as shown in Figure 4, the dynamic sealing pressure is 14- ~ 35MPa; static sealing pressure is 70MPa. Tubing and coupling, is in the BOP sealing conditions, together with the lifting and BOP, cylinder and rotary slips, no relative motion between the oil and the BOP pieces of sealant, the whole cylinder is derived by taking off and landing of tubing, one of the greatest travel up to 10m.

Figure 4 high pressure operation device with pressure
1 liquid discharging Jane, 2 bearing kava, 3 cross member assembly, 4 propping prevention kava, 5.Fm2-21 annular BOP, 6 small, 7 expansion joint assembly, 8 beam assembly, 9 lifting oil cylinder, propping prevention kava 10 enclosed bearing, 11.FHl8-35 annular BOP, 12 transverse beams assembly, 13 three ram blowout preventer,14 hole four.