The Research Of Technology On Old Well Drilling Deeper With Coiled Tubing

Coiled tubing (CT) is by using a special process to weld flexible pipes which are made through a special forging process. According to the needs, it’s length could be from a few hundred meters to several kilometers. The coiled tubing is also called flexible tube, the serpentine tubes or coils. All the equipment of coiled tubing is called Coiled Tubing Unit (CTU). Coiled Tubing Drilling (CTD) is a new kind of drilling technology with the CTU and a series of downhole tools to prospect and develop the oil and gas well. Today, many of the oil fields have entered a late stage of development in the world, especially our most of mainland oilfields, a sharp decline in production, have been the high-water-cut well, and lead to a sharp decline in production. In addition, due to the impact of equipment and drilling technology, there are a considerable number of low-permeability and special oils and gas reservoir has not been developed.CTD technology is definitely a good way to solve such problems.CTD is drilling technology by using coiled tubing instead of conventional drill pipe.Coiled tubing itself has no joints, no variable diameter, bending, continuous tripping, dynamic packing, high intensity, high pressure resistance, small size and easy transportation characteristics.This technique does not require stopping the pump and make a connection in the drilling process, and can achieve the continuous circulation of the drilling fluid, improve the speed of tripping and job security, reduce the drilling time and drilling cycle.The old oil fields, by using the CTD technical to reentrant deepen or sidetrack, not only can save the cost of drilling, but also can be found and develop the new reserves, contribute to the stable output of old oil fields, enhance oil recovery and increase oilfield efficiency. CTD technology can take the slim hole drilling, underbalanced drilling, low pressure loss layer drilling.CTD underbalanced drilling technology can be safely and easily to improve drilling success rate. For water-sensitive and collapse layer, CTD technology can be used nitrogen gas drilling and oil-based drilling fluids, which are a safe and reliable drilling technology for special gas such as coalbed methane and shale gas reservoirs. Combined with the significant professional project of the National Science and Technology (task6of Project36)"The coiled tubing equipment and the application of technology" research the process for coiled tubing old wells deepened. The purpose of the study is very important, the research results can be used to guide the field of coiled tubing drilling test, and initially formed the process of research reports for the old well drilling deeper with CTD, and make some contribution to the development and improvement of CTD technology. CTD is a new drilling technology in our country. The conducts of CTD is the first research in this paper, have been accepted by the China National Petroleum Corporation (CNPC), and could successful to guide the first well of CTD in our county. In this paper, all the research methods and research results obtained are as follows:(1) In this paper, all the CTD required equipment and tools are summarized, and detailedly described the functional and technical parameters of important equipment and tools. Because of the CT will withstand the three bending-stretching alternating stress in each time of construction process, the CT is very easy to fatigue damage, and will lead to a relatively short lifespan. This fatigue failure is the low cycle fatigue. The relevant experiments indicate that CT fatigue cycles not only depend on the size and the radius of curvature.The higher internal pressure will greatly reduce the cycles of the CT.(2) Principle of rock-breaking of PDC bit is studied. The static physical model of rock breaking is established. The construction parameters of the small size bit (Φ118) and mechanical specification for Ma758well are given:bit on weight30KN; rotation rate150-180rpm.(3) Coiled tubing drilling downhole tools are analyzed. And make a lot of detailed explanation for the main tool.On the basis of the existing well structure of the ma758test well, the bottom hole assembly (BHA) for old well drilling deeper are recommended. Checked on the strength of the entire CT drillstring, and analysed the dangerous stress points, the calculation show that the CT drillstring is safe.(4) Fluid mechanical characteristic of CT is discussed; pressure drop is calculated in detail, including the reel, well and BHA. Considering the capacity of carrying cuttings and wellbore stability, and the technical parameters of the small size of helicoid hydraulic motor and drilling pump, pump displacement and circulating total pressure loss for the test well is accounted.(5) To combine the special construction of CT and the experiences of workover and completion operations in the field, tentatively set the construction process of the treatment specification for the old wells deepened in CTD.