Researches On Fluid-dynamic Parameters Of Pneumatic DTH Hammer Reverse Circulation Drilling System Used In Oil-Gas Exploration

The continued high-speed development of national economy pushes the oil-gas consumption to growth. The supply-demand relationship of oil and gas gradual becomes imbalance. It is an urgent need for national economic development to increase proven oil-gas reserves and increase oil-gas output. But, the majority oilfields explorations are in the mid-late stage, and most are "difficult-to-produce" reserves, which is difficult to be found and be exploited. Only low-voltage, low-permeability oil and gas fields have the exploitation potentiality. The facts showe that it is hard to effectively prospect and exploit "difficult-to-produce" reserves with existing conventional drilling technologies. Therefore, we can draw on technological progress to make "difficult to produce" oil-gas resources converting to "available" oil-gas resources. The pneumatic down the hole hammer (DTH) reverse circulation drilling technology is an new effective approach.The pneumatic DTH reverse circulation drilling technology was the important branch of the gas drilling technology, China with independent property rights. With the whole process into reverse circulation drilling craft, it was a high technology combined with three techniques-DTH hammer impacting breaking rock, fluid medium full hole reverse circulation and continuous obtaining rock core sample-into one system, and was evaluated the international advanced drilling technology by experts. At present, the DTH hammers have been formed series specification, and tens of matching reverse-circulation drill bits could meet the requirements of the different formation drilling. As the drilling process and the outfitting tools gradually become maturation, the pneumatic DTH reverse circulation drilling technology has got more widely applied in the solid mineral exploration and hydrology water well drill. These laid the foundation for this technology applying to oil and gas exploration and development field. The paper supported by the project of "feasible study on air reverse circulation drilling system ", the work that in so far as characteristics of oil and gas exploration and requirements of the pneumatic DTH reverse circulation drilling technology conducted researches on fluid-dynamic parameters of pneumatic DTH hammer reverse circulation drilling system. Around the gas reverse circulation drilling temperature model, the circulatory system pressure and the selection of gas injection parameter, the paper was undertaking a study to resolve gas regulation issues caused by deep well, large diameter and so on, in order that was supplied the favorable technical support when the pneumatic DTH reverse circulation drilling technology was applied in the oil and gas exploration drill field. The main research contents and conclusions were the following:1.It was systematicly introducing the pneumatic DTH reverse circulation drilling technique used in oil-gas exploration and drill system components. With regard for the current situations of oil-gas exploration field exploration and development, it was analyzed the potential advantages and what was needed is a research on fluid dynamics parameters. Based on the existing gas drilling theoretical studies at home and abroad, it was developed researches on fluid-dynamic parameters, on the leverl of mathematic theoretical deriving to build air reverse circulation drilling temperature calculation model, pressure calculation model, gas injection rate calculation model.(1)On the basis of the existing gas drilling theoretical studies, the heat exchanges between the drill string fluid, the annulus fluid and the formation were considered when establishing the gas reverse circulation drilling temperature model in progess.(2)And then with the order of gas flowing through the pipeline to establish the whole circulatory system pressure calculation model, which could get the whole down hole circulatory system pressure distribution law by calculating.(3)It was built the pneumatic DTH reverse circulation drilling gas injection circulation model, according to which the gas could be regulated with the increasing hole depth, so to guarantee DTH's normal work in the hole bottom.2.When the theoretical models were deduced, there were some assumed conditions of compressed gas flowing in hole bottom, so the auther desigened the reverse circulation bottom compressed air flow test bench. As far as these conditions were concerned, it was developed the reverses on reverse circulation drilling gas fluid-dynamic parameters. Through experiments on the cutting element bottom exposure, spiral type and central type inner pipe with different diameters nozzle flow field, eight sets of different combination of nozzles and bottom jet holes, the main research contents were the following: (1)To adjust the support screw height was to adjust the distance between the drill bit labial surface and the hole bottom, so it could research on the change relation between the cutting element bottom exposure and hole bottom flow field.(2)Under the conditions of nozzles and bottom jet holes arranged in different combinations, by measuring the circle gap flow rate to analyze the hole bottom flow field variation, so further to analysis on the reverse circulation mechanism.(3)By the premise of the reverse circulation drill bit labial surface chosen as concave shape, it was tested the difference between flow fields generated by spiral type and central type inner pipe with different diameters nozzle.3.With CFD software, establishing the reasonable physical and mathematical model, the pneumatic DTH reverse circulation drilling hole bottom flow field was got simulated, and truly represented the flow pattern of the reverse circulation drill hole bottom local flow field. Furthermore, it was to know in detail the structural characteristics of the hole bottom reverse circulation flow field, so to reveal effects between the cutting element bottom exposure, inner nozzle angle, bottom jet hole centre distance and the hole bottom fluid dynamic parameters.(1)Different centre distance bottom jet hole flow field simulation. The numerical simulation showed that as far as GQ-320 type bottom drill were concerned, there were about 1.1% that the change of the bottom jet hole centre distance had effect on hole bottom air volume.(2)Different types and different diameters nozzles flow field were simulated. The distribution of the hole bottom flow field was directly impacted by the nozzle diameter. Combined with the actual drilling conditions, it was determined by tyoes and diameters that the air model was whether to amend.(3)The cutting element bottom exposure was simulated. The compressed air jetted from the bottom jet hole, some gas was upwards going along the circle gap. The result of the numerical simulation was consistent with the experimental result.(4)The key point numerical simulation and centralizer structure optimization. Flow field characteristics of the centralizer parts are analyzed, and the hexagon centralizer was optimized design by CFD technology, which was reducing the pressure loss of the key points.The above conclusions and understandings provided important basises to establish the correction factor of calculation models. Eventually, it was established the oil-gas exploration pneumatic DTH reverse circulation drilling fluid-dynamic parameters calculation system. 4.Based on GQ-320 type pneumatic DTH reverse circulation drilling system, program modules of the temperature model, the pressure model and the gas model were programmed by using mathematical software MATLAB, so a set of air parameter calculation system of the pneumatic DTH reverse circulation drilling was established. The results counted out according to the procedure were achieved good results with field application, and it was realized the real-time control on the ground gas supply quantum of drilling operations during the course of oil drilling.The main creative point in this paper includes:(1)On the basis of the existing gas drilling temperature theoretical studies, the heat exchanges between the drill string fluid, the annulus fluid and the formation were considered, when establishing the gas reverse circulation drilling temperature model in progess for the first time.(2)Based on the pneumatic DTH reverse circulation drilling pressure calculation model was established, and integrated the minimum speed law, the minimum kinetic energy law and the minimum bottom-hole pressure method, it was firstly built the pneumatic DTH reverse circulation drilling gas injection circulation model.(3)It was firstly studied the effects between cutting edges and the reverse circulation, and designed the reverse circulation bottom compressed air flow tester. Experiments showed that cutting edges had little effects on fluid-dynamic parameters, and CFD simulation revealed the mechanism between cutting edges and the reverse circulation.(4)Flow field characteristics of the centralizer parts are simulated, and innobatived several shapes. According to numerical simulation, the hexagon centralizer was optimized design which was reducing the pressure loss of the key points.At present, fluid-dynamic parameters of pneumatic DTH hammer reverse circulation drilling system still remains in the level of theoretical derivation, laboratory test and numerical simulation, and yet to be tested and revised by actual drilling. The above content in this paper are just the preliminary fundamental research about the technical problem of the compressed air changing when the pneumatic DTH reverse circulation drilling used in oil-gas exploration field. Further more, it is need to deeply comprehensive research on the pneumatic DTH reverse circulation drilling Introduced into the field of oil and gas exploration.