Study on drilling method

At present, the advanced drilling methods mainly used at home and abroad include diamond wireline coring drilling, hydraulic hammer percussion rotary drilling, power hammer reverse circulation drilling and foam drilling.

(1) diamond rope coring drilling

In geological exploration drilling construction all over the world, the most widely used drilling technology with the best comprehensive geological effect is mainly diamond rope coring drilling technology. Wireline coring drilling technology (WL) was first born in the oil drilling industry in the 1940s, and was improved and developed by Longyear Company of the United States, and applied to the core drilling construction of solid minerals. Since then, it has been widely used in the world and has a history of nearly 70 years. The birth and successful application of WL drilling technology has realized coring without drilling and greatly improved drilling efficiency, which is called a revolution of geological core drilling technology [24, 25].

Foreign countries have always attached importance to and constantly developed and improved the diamond WL drilling technology. The material selection, machining accuracy, heat treatment and geometric size of drill pipe are studied emphatically, which further improves the strength and toughness of drill pipe and the reliability of connecting thread. At the same time, the diamond bit is deeply studied, which improves the life and drilling efficiency of the bit.

Since the mid-1970s, China has begun to study and popularize the application of diamond WL drilling technology, which has played an important role in geological prospecting. By the end of 1990, the drilling workload reached 1505 m, the drilling speed and monthly efficiency were greatly improved, and remarkable economic and social benefits were achieved. This technology is almost universal in the national prospecting field, and thus won the first prize of national scientific and technological progress [65438]. However, in the ten years since 1992, due to the sharp reduction of mineral exploration workload and the transformation of drilling construction units to the building foundation field, the application of diamond WL drilling technology has also decreased significantly, resulting in the very slow development of this technology, even stagnation, and the gap with advanced foreign countries has further widened. There are obvious gaps in the service life, reliability, drilling efficiency and drilling depth of WL drilling drill pipe, and the core drilling workload completed by WL drilling technology is less than all. In recent years, with the rise of a new wave of geological prospecting, this technology has been restored and developed, and its application breadth and depth have been further expanded. The provincial geological prospecting bureau, represented by Shandong and Hebei, further popularized and improved this technology, which played a prominent role in "digging deep to find blindness" and improving efficiency. Many indicators such as drilling depth and drilling efficiency have been continuously broken, and the technical level has been greatly improved.

(2) hydraulic hammer percussive rotary drilling

Foreign countries have always attached importance to the development of hydraulic percussion rotary drilling technology. DTH hydraulic impactor (also known as hydraulic DTH hammer, hereinafter referred to as hydraulic hammer) originated in Europe. 1887, German Walter bushman obtained a patent for a new drilling method in Britain. The core of this technology is to use the liquid energy supplied by the pump to drive the hydraulic impactor to continuously impact the rotating drill bit, so as to realize impact rotary drilling. Since 1950s, the United States, Canada and the former Soviet Union have developed several practical hydraulic impactors. In terms of geological and mineral drilling, the most effective research is the former Soviet Union. 1900 ~ 1905 carried out the research on hydraulic percussion rotary drilling technology, and 1970 began to be gradually applied to production practice. In 1960s, Hungary developed five kinds of φ 48 ~ 160mm double-acting hydraulic impactors. Hydraulic percussion drilling tools are assembled on special trailers and equipped with corresponding pumps, desanders, coring tools, drill bits and accident handling tools, which are flexible and convenient to carry and can serve multiple drilling rigs in construction mines or construction sites. Japanese research on hydraulic impactor began in 1970s, and WH- 120N double-acting hydraulic impactor developed by Li Gen Company was successful. Its greatest feature is that it uses gas and liquid as working fluids [14].

In recent years, there is relatively little research work in hydraulic hammer abroad, mainly including the double-acting hydraulic hammer developed by Pan American Oil Company, the FH series hydraulic hammer developed by Australian SDS Company, and the composite hydraulic hammer (with positive pressure valve and double-acting impact hammer) made by Kloster University in Germany (intended for KTB project in Germany, but not adopted), all of which are driven by clean water (100μm filtration). Because the washing liquid can not effectively protect the wall, the depth of use is limited, and the deepest application record is only 590m·m m.

China began to study from the end of 1958, and by the end of 1980s, China's research on hydraulic hammer reached its peak. Geological and metallurgical departments have developed various types and specifications of hydraulic hammer for small-diameter coring drilling, including forward-acting, double-acting, reaction and compound hydraulic hammer. All models have reached more than 30 kinds, and the cumulative footage has exceeded one million meters, realizing good technology. Rough statistics can improve drilling efficiency by 30% ~ 50%, at the same time, it can obviously improve drilling quality and core recovery rate, extend footage and reduce material consumption. At present, the research and application level of hydraulic hammer in China has reached the advanced level in the world, and it is the country that has widely applied hydraulic hammer drilling technology in the field of small-caliber mineral exploration after the former Soviet Union [14,26].

In 1990s, due to the sharp decrease of geological exploration workload in China, the research investment in small-caliber hydraulic hammer was almost interrupted, and these achievements were not well applied and perfected. The research and application of this technology turned to the research of large-caliber hydraulic hammer for hydrological wells, oil fields and engineering construction. Until 1997, the Institute of Exploration Technology of China Geological Survey developed a new YZX series hydraulic hammer (Figure 1-3), and its static sealing reliability, high temperature resistance and adaptability to deep hole back pressure were improved and improved. Especially in the scientific drilling project in Chinese mainland, the YZX 127 hydraulic hammer they developed has been drilled for nearly 500 times continuously, creating a world record of the total footage of a single well in a complex mud environment of 3,485.71m and the maximum application depth of 5118.2m.. In addition, the Institute of Exploration Technology has also developed KS- 1 57 wireline coring hydraulic hammer, SYZX273 hydraulic hammer and screw motor/hydraulic hammer /WL- three-in-one drilling tools for continental scientific drilling and exploration engineering, all of which have been successful and played an important role in improving drilling efficiency, preventing core blockage, prolonging return footage and reducing well deviation [14].

Figure 1-3 New YZX Series hydraulic hammer

The successful application of this technology in Kezuan 1 well has promoted the progress of drilling technology in China. At the same time, the Continental Scientific Drilling Project has also played a very important role in promoting the great development of hydraulic hammer's drilling technology, making China's deep-hole hydraulic hammer drilling technology reach the international leading level, which has been highly praised by many foreign counterparts. German, Australian, American and other companies have introduced this technology from China for experimental research. But up to now, the largest hole depth of coring drilling in hydraulic hammer abroad is 2000m, which was created by the former Soviet Union (no detailed information is reported). Australian SDS Company cooperated with PDVSA Company to test the maximum hole depth of hydraulic hammer's full-scale drilling in the interval of 4333.03 ~ 4353. 15 m of PIC26 well. Generally speaking, hydraulic hammer for deep wells is still in the stage of research and test, and has not reached the level of large-scale application. The theoretical analysis and research on the working performance of hydraulic hammer under deep hole conditions in China need to be further deepened. Especially under the ordinary production conditions of small-diameter drilling in solid minerals, the solid control system of mud still stays at the level of traditional natural precipitation of rock powder. During drilling, the solid content of mud is high, which leads to frequent jamming of internal parts in hydraulic hammer and greatly reduces the working life, thus leading to frequent drilling. In the process of popularization, although the advantages of hydraulic hammer drilling are recognized and accepted by everyone, its practical application is still relatively small [14,28].

(3) Reverse circulation drilling with power hammer

In many countries, reverse circulation drilling technology of pneumatic DTH hammer (hereinafter referred to as power hammer) has also been greatly developed. There are mainly two kinds of this technology, one is through common power hammer+cross-channel joint+double-arm drill pipe, that is, RC or CSR drilling technology; The other is realized by a through-hole power hammer with RC coring bit and double-arm drill pipe, that is, through-hole RC drilling technology. Because the power hammer RC drilling technology has changed the traditional rock-breaking coring method, its drilling efficiency can be improved by 3 ~ 10 times, and the cost can be reduced by 1/2 ~ 2/3. Therefore, the power hammer RC drilling technology is called another revolution after WL drilling technology by the drilling industry [16,29]. As early as the mid-1980s, the United States, Canada, Australia and other countries studied, developed and widely applied this technology in the exploration stage. Samplex-500 is a valveless through-hole power hammer developed by the United States in 1989, which has been used on CSR rigs by major drilling companies [30]. At present, there are more than 65,438+050 power hammer RC drilling equipment used in various geological and mineral exploration, including placer gold and rock gold deposits. It is reported that the proportion of geological drilling completed by power hammer RC drilling technology has exceeded 80% in Australia, nearly 80% in the United States, nearly 60% in Southeast Asia and nearly 30% in Africa. Some mining areas almost all adopt electric hammer RC continuous sampling drilling method, or the ratio of electric hammer RC continuous sampling drilling to WL drilling workload is 20: 1. The maximum hole depth of RC drilling with electric hammer has exceeded 700 m [16].

China has been studying this technology since 1980s. The exploration technology research institute and other units have studied the common short-hole hammer RC or CSR drilling technology. 1987 imported Canadian drilling rig for CSR drilling test, and successively developed special equipment, double-walled drill pipes with different specifications and auxiliary devices, which were applied in individual mining areas. The former Changchun Institute of Geology studied the RC drilling technology of through-hole DTH hammer, and successively developed GQ series through-hole DTH hammer and corresponding RC coring bit. Especially, a lot of research work has been done on RC mechanism, injector principle and internal flow field of RC coring bit, and many research results have been obtained. However, because the domestic geological community has not recognized the use of cuttings instead of traditional columnar cores for mineral resources evaluation, there is no corresponding standard to follow at present, and this technology can not be adopted in geological drilling design, so this technology has not been popularized and applied. Only when the strata in the mining area are particularly complex, it is impossible to drill and core, and then the experimental application is carried out. For example, in the geological exploration of complex strata such as Sandaozhuang molybdenum mine in Luanchuan county, Henan province, Songxian gold mine in Henan province, Baiganhu tungsten-tin mine in Xinjiang, RC drilling technology with electric hammer is adopted. In addition, some mining areas funded by foreign mining companies, such as Australian Ruixiang Company, require the adoption of RC drilling technology in the exploration of Zhengguangyan gold deposit in Nenjiang, Heilongjiang. After the application, remarkable technical and economic benefits have been achieved, the drilling efficiency has been improved by 3 ~ 10 times, and the cost has been reduced by 1/2 ~ 2/3 [29].

(4) Foam drilling

Foam used in drilling engineering began in the mid-1950s. At that time, in order to drill in dry and unstable formations, Nevada first used foam drilling fluid. Because the upward speed of foam drilling is only110 ~1/20 of that of air drilling, the stability of the hole wall is effectively guaranteed. Since then, the United States has further carried out research on foam fluid suitable for drilling in salt water, oil layer and permafrost layer, expanded the application scope of foam drilling, and achieved good economic benefits, becoming an effective means of developing low-pressure oil fields.

The former Soviet Union began the experimental study of foam drilling in the early 1960s. In 1970s, small-diameter diamond coring drilling started with foam, and the rheological properties, temperature and pressure of foam during foam drilling were deeply studied theoretically. After more than ten years of preliminary research, it has been proved that compared with conventional flushing fluid, the penetration rate of drilling rig is increased by 30%, the footage of drilling times is increased by 22.5%, the drilling efficiency is increased by 25%, the diamond consumption is reduced by 28%, the power consumption is reduced by 23%, and the comprehensive economic benefit is increased by 34%. By 1984, the drilling workload of foam drilling technology in the former Soviet Union was close to 10× 104m, and the supply of various foaming agents was 60 ~ 70t [3 1 32].

In the United States, Canada, Germany, Britain and other countries, foam drilling technology has also developed rapidly and is listed as the direction of new technology development in the future. In the early 1980s, the United States basically completed the research work of foam drilling. 1980, Sandia National Company developed 100 kinds of cationic, anionic, composite and nonionic foaming agents to meet the needs of foam drilling under various complex formation conditions. Foam drilling equipment has reached serialization; Drilling technology has reached the level of computer control.

The research on this technology started late in China. In the mid-1980s, foam was first used for well washing and drilling in petroleum system, and foaming agents such as F873 and TAS were developed. Since then, geological and coal systems have also carried out research work in this field, and successively developed KZF 123, CD- 1, CDT-8 12, CDT-8 13, DF- 1 and ADF-. However, due to the sharp reduction of geological drilling workload, the initial investment, energy consumption and foam recovery cost of this technology are higher than those of ordinary drilling technology, which leads to the stagnation of its popularization and application. Until the middle and late 1990s, changchun university of science and technology initiated a project in the former Ministry of Geology and Mineral Resources to study the foam booster device of water pump, and achieved the effect that the volumetric efficiency of foam booster pump reached 90%. In 2000, in order to cooperate with the western development, on the basis of the above research, a large-scale water pump pressurized foam perfusion system was specially developed. After the actual construction test in Xihaigu area of Ningxia, the pumping capacity of the pump has reached 5MPa, which is gratifying [3 1 32]. In addition, Jilin Science and Technology Commission has started the special research on foam DTH hammer, and made a breakthrough, but further experimental research and improvement are needed before it can be used in production.