| The hollow-through type DTH hammer drilling has an incomparably priority to traditional rotary drilling methods in the aspect of penetration efficiency. It was also called down-the hole hammer rock drilling tolls which possessed with the special structure form. The hollow- -through type DTH hammer with the whole process into the reverse circulation drilling craft, which was relative to the hollow-trough type DTH hammer,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 had got more widely applied in the solid mineral exporation and hydrology water well drill. At present, the DTH hammer has been formed into a specification series. The drilling process and the outfitting tools gradually become maturation, so the application area is continuously extended and has a broad prospect. The hollow-through type DTH hammer drilling technique with its own unique technique advantages, could supply for the favorable technical support to solve the efficient development problems of the low-pressure, low permeability and low yield reservoir faced in the oil and gas exploration drill field currently, and to enhance the drill speed of the complex strata and the deep well ground consisted of hard rock.The paper supported by the project of"feasible research on air reverse circulation drilling system", carried out the technique research on the establishment of mathematical model for the hollow-through type DTH hammer drilling process. On the way of combining the test data got from productibility field test with the numerical simulation and the theoretic research, the paper established a wearing function of drill bit and the mathematical model of drilling process, and carried out the technique research on the method for selecting optimal drilling parameters of the hollow-through type DTH hammer drilling process, as a result it could be the a guide of the practical drilling operation.The main research contents and conclusions are as following:(1) Based on the analysis of the hollow-through type DTH drill technology's characteristics and on the analysis of technical problem for importing the hollow-through type DTH drill technology into the deep well drill especially, the paper presented the implementation of optimal control of the hollow-through type DTH drilling process, so as to apply the hollow-through type DTH hammer drilling crafts of the whole process reverse circulation for the oil and gas exploration successfully.(2) The paper discussed the destruct character, dynamic analysis, crack expanding, destruct volume and the relation between the cumulate damage and the impact number of rock under many kinds of loading condition. Some conculsions got from theoretic analysis could be gave as a basis for selecting optimal drilling parameters: The time of loading the impact energy when the both of a static pressure and a impact cooperate, is the moment of that the rock breaks in solid, the rock debris are out and the compact entity is pressed fully. The point is in the sect of load–incursive depth curve which a slope is negative, and the best loading range can be confirmed by an experiment. This loading rule has important directive function for selecting the drilling parameter. The cut-in force composes by the both of a static pressure and an impact, and has a direct ratio with them. Impact energy in the cut-in force is in the pattern of wave which can be influenced by rock's character and parameter of breaking rock, so the perfect effect of breaking rock in different kinds of rock need different breaking rock parameter.(3) The paper observed the condition of worn cemented carbide-drill bit buttons by a scanning electron microscopy (SEM) for the DTH hammer drilling carefully, conbined it with previous papers, and presented both of the new five classes of deterioration mechanism and the five calsses of material removal mechanism of drill bit buttons for DTH hammer drilling. The deterioration mechanism includes the five classes: Composite-scale crack formation;WC grain-scale crack formation; Oxidation and corrosion of WC grains;Embrittlement and degradation of the binder phase;and rock cover formation, rock intermixing and rock penetraion. Wear mechanism includes the five classes: Crushing of WC grains and release of fragments; Detachment of whole or parts of WC grains; Crushing and removal of bineder/rock mixture; Tribochemical wear of the carbides; Detachment of composite-scale fragments.(4) In accordance with the demand of the reasonable controlling of real drilling process, the paper established a wearing function of drill bit and the mathematical model of drilling process as a function of controllable parameters, and typically by exemplifying the traditional rotary drilling methods of the diamond impregnated drilling bit, discussed the relationship between optimal drilling parameters of the every optimization goals. Under the normal condition of the rate of penetration (ROP) value varing as time increases, the four optimal goals (ex. maxium ROP, maxium drill velocity per round trip, maxium drill length per drill bit and minium drilling cost per meter) and their optimal drilling parameters could be selected. From qmin-goal, in the case of a shallow drill depth, the difference of drilling parameters between the qmin-goal and the Vmax is not so cosiderable, but as a drill depth increases, the difference also increases.(5) According to detailed analysis of the principal infulence factors to the ROP and the basic theoretic research of the artificial neural network, two multilayer neural networks with back propagation algorithm(BPNN), i.e Feedforward BP network and Cascade feedfoward network have been employed to predict the ROP of the hollow-through type DTH hammer drilling process, and the number of hidden layers and the number of neural cells in the neural network have been defined, so as to carry out trainning and testing by the established neural network. At the same time, drilling parameters have been optimized to guide the penetration operation based on the prediction results.(6) Based on the wearing function of drill bit and the predicted ROP value by neural network,the infulence of drilling parameters to the drilling technology- economical indices has been analyzed. In the case of a shallow drill depth ( tBC / t≦), the goal of the minimum drilling cost per meter(qmin)and the goal of the maximum ROP(Vmax)are basically equal, so to increase ROP is a resonable drilling method. But in the deep well drilling process, goal of the Vmax is not so reasonabe, and either the goal of the qmin or the goal of the hmax is reasonable.The main creative point in this paper includes:(1) The condition of worn cemented carbide-drill bit buttons by a scanning electron microscopy (SEM) for the DTH hammer drilling has been observed cautiously and conbined with previous research, and the new five classes of deterioration mechanism and the five classes of material removal mechanism of drill bit buttons for DTH hammer drilling have been presented.(2) In accordance with the demand of the reasonable controlling of real drilling process, a wearing function of drill bit and the mathamatical model of drilling process have been established as a function of controllable parameters.(3) Based on the wearing function of drill bit and the prediction of the ROP value by a neural network, a new selecting method of optimal parameters for the DTH hammer drilling process has been established.Now, for the purpose of increasing the drilling technology-economic indices of the hollow-through type DTH hammer drilling and applying it to a deep well drill, by using the diamond-enhanced tungsten carbide composite button bits, a professional reverse circulation drill bit is designed, the pratical test of its drilling efficiency is going to be taken, and we must research it further.
|
PDF Full Text Request