| Kuqa piedmont structures is the key of the Sinopec exploration and development blocks, as an important force to speed up the construction of oil and gas in western China, has a broad development prospects. But with the increase in natural gas exploration and development efforts in China, the development is also becoming more and more difficult. Practice shows that in the area of the tarim basin, the more the difficulties encountered in the process of drilling, main show is high formation drilling resistance and low rate of penetration, long drilling cycle, etc. Therefore, efforts to improve the rate of penetration and improve drilling efficiency, shorten the construction period, the efficient use of energy to piedmont tectonic region have important practical significance.This study is based on petroleum engineering pilot and promotion project named " Research of Kuqa piedmont region safe optimized drilling technology " Based on the kuqa piedmont region complex geological conditions, in view of the piedmont structure in the process of exploration and the prevalence of bit wear fast, slow drilling speed, the in-depth study of piedmont tectonic formation drilling resistance characteristics of region, summarizes the formation drilling resistance patterns. From the viewpoint of mechanics, the mechanical behavior of a detailed analysis of the rock breaking tools, combined with the practice, to optimize the selection of rock breaking tools, And the introduction of specific design concept, based on the theoretical model, designed to adapt to the complex stratum rock breaking tool thrust, eventually forming a set speed scheme suitable for piedmont tectonic region. The main results of the study are as follows:(1) In the conventional indoor micro drill method to establish the formation drillability calculated based on the model. Use of formation rock hardness tester acoustic logging are analyzed and the mathematical relationship between rock hardness, considering the rock hardness on the analysis of the kuqa piedmont region in the study of formation drilling resistance, kuqa piedmont structure formation has been established calculation model of the drilling resistance of rocks, through the test and analysis of the whole strata in the Kuqa area drilling resistance law, and draw the Kuqa Piedmont region formation drilling characteristics of distribution. Through the analysis of formation of Kuqa piedmont drillability and rock hardness is generally increased with increasing depth, but in the Quaternary strata and Jidike formation and the Cretaceous the fluctuations of drilling level and hardness greatly, Quaternary strata of drillability grade value range between 1～6, formation rock hardness between 10Mpa～500Mpa, JiDiKe group and under the cretaceous formation drillability grade value range between 3.5-6, formation rock hardness between 250Mpa～1000Mpa.(2) From the point of view of mechanics research and analysis the force of the rock bit and PDC bit and the rock fragmentation mechanism of the combination of research on the regular of the formation drilling resistance characteristics and geological condition of Kuqa piedmont region. Summarized the Kuqa piedmont tectonic area application scope and characteristics of drill bit, and then in-depth analysis is suitable for the Kuqa piedmont region of bit type selection theory, based on the theory of completed the Kuqa piedmont region of bit type selection, formed a set of suitable for the bit sequence of Kuqa piedmont tectonic regions. Quaternary strata due to the thick gravel, formation drilling resistance is strong, use roller bit more, Kuqa and JiDiKe group stratum, formation mainly mudstone, formation drilling resistance is good, suitable for power at the bottom of the hole drilling with PDC bit, it is recommended to use less number of blade, low density bit teeth. JiDiKe group and SuWeiYi formation due to the formation containing a large section of the salt-gypsum rock, in the actual bit in use, the effect is not ideal, But as a result of the formation has a little difference with upper strata hardness, and the first in the group JiDiKe formation have significantly lower hardness trend, on the selection of drill bit still choose 5 blade bit, to ensure that bit of aggression. Considering the formation drillability is poorer, less bit cutter size, by 19 mm to 16 mm, in order to improve the service life of cutter. Cretaceous strata due to poor formation drilling resistance, obviously harder the formation of abrasives, stratigraphic interlayer from the upper strata increased obviously, stratigraphic lithology change is great, should be chosen on the selection of drill bit has high wear-resisting tooth bit, such as DFS1605U drilling in the layer has good performance, the average rate of penetration of 2.05 m/h, than ordinary PDC bit mechanical drilling rate increased by 49%.(3) According to the usage of the bit has been drilling in complex strata, the comprehensive analysis of the quaternary thick gravel layer and JiDiKe group bit using characteristics of large section of the salt-gypsum layer, the bit has been optimized design. Quaternary strata mainly adopts cone bit, by improved bit nozzle, strengthen the dorsal metacarpal, optimization of tooth profile, in order to improve the bit in the Quaternary strata of rock break ability. Analysis theory of PDC bit design, in view of the PDC bit in JiDiKe group formation in the process of the use of common teeth attack is not strong, poor impact resistance, From the cutter, blade, crown shape, size to protect this a few aspects, designed a 16 mm cutter,5 blade, medium parabolic type, medium density cloth tooth T1653 drill bits, and use at the scene of the kuqa 2 well, have achieved good application effect.Through the above research achievements, have a certain understanding of the Kuqa piedmont structures and stratigraphic characteristics, formed a set of bit optimization scheme, provide guidance for the well drilling in this area. |
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