Progress and development of particle jet drilling speed-increasing technology and rock-breaking mechanism for deep well

Increasing drilling speed and efficiency of hard formation for deep and ultra-deep well is one of the international recognized drilling problems and key technologies to be tackled urgently. Particle jet impact drilling technology is an efficient non-contact rock-breaking method to overcome slow drilling speed, which has great development and application potential in drilling speed-increase of hard formation and deep well. High efficiency drilling technology and rock-breaking speed-increase mechanism in high temperature, high pressure and high hardness formations of deep and ultra-deep wells were mainly focused and keynoted in this paper. With extensive investigation of domestic and foreign literature, the working principle, key technical devices, deep-well-rock mechanical characteristic, unconventional constitutive model and rock-breaking mechanism of particle jet impact drilling technology were analyzed, which proved the feasibility and high efficiency for deep and hard stratum, and also, dynamic failure mechanism of rock needs to be elaborated by constructing the constitutive model with high temperature and pressure. Meanwhile, the major problems to be solved at present and development direction future were summarized, which mainly included: miniaturization of drilling equipment and individualization of drilling bit; optimization of jet parameters and the evaluation method of rock-breaking effect; establishment of mechanical property and unconventional constitutive model of deep-well-rock; rock-breaking mechanism and dynamic response under particle jet coupling impact. The research can help for better understanding of deep-well drilling speed-increasing technology and also promote the development and engineering application of particle jet impact drilling speed-increase theory and equipment.

Experimental simulation of proppant permeability in hydraulic fracturing at extended time under bottom-hole conditions

During hydraulic fracturing treatment, huge quantities of gel are pumped into the formation to initiate the fracture, maintain it open and transport the proppant. The fracture dimensionless conductivity (Fcd) is a key parameter to optimize the fracturing design, to estimate the productivity Index (PI) and the folds of increase (FOI). However, these parameters are affected by the gel residues which decrease the fracture conductivity; thus, the proppant cleanup is a very important step to avoid additional damage caused by fracturing fluid due to high gel concentration and the extended time of gel staying in the fracture before cleanup. Throughout the life of Hassi Messaoud, Algeria field, hydraulic fracturing technique has been aggressively used mainly in four producing formations in the Cambrian, with hard formation characteristics, an average permeability range and low reservoir pressure (0.15–0.45 psi/ft) and high stress value between 6000 and 9000 psi. In this paper, an experimental simulation is applied using a self-made cell to determine the effect of different parameters on the fracture conductivity under various bottom-hole conditions where different variables were used: effect of Proppant type, guar gel concentration, temperature, breaker concentration and closure pressure at extended time. An important drop in fracture conductivity was observed varied between 10 and 80% under stresses at interval of 2000 psi and 8000 psi, gel concentration up to 200 lb/1000 gal at extended time and temperature.

Selective insulation of water flows in a well based on the use of production waste

A method for isolating water inflows into the well by blocking high permeability zones with a gel-forming composition based on sodium silicate, including biologically active additives has been developed. Whey is used as a biologically active supplement. As a result of isolation of the watering intervals by the gel-forming composition, low-permeability oil-saturated areas are involved in the development. The gelation process can be adjusted depending on the concentrations of sodium silicate and whey, as well as the temperature at a certain depth of the reservoir, necessary for isolation. In order to prevent a premature coagulation process when the formation is saturated with hard formation water, fresh or softened water is pumped in front of the gel-forming composition. This technology is used to reach the residual resistance factor to the value 3.88, an increase in oil production will be 18.5%.

Investigation on the effect of changing rotary speed and weight bit on PCD cutter wear

The research is to determine the optimum range of rotary speed and weight-on-bit value for interbedded formation to reduce PCD cutter wear rate. To simulate an interbedded formation, a combination of limestone as the soft formation and granite as the hard formation is selected. The research is conducted based on analysis of cutter-rock interaction model, wear model and simulation of PCD cutter using finite element analysis in ABAQUS software. The results show that the optimum range of weight on bit and rotary speed for limestone is between 1000 N, 21.4 RPM, and 4000 N, 85.6 RPM, while for granite it is between 1000 N, 21.4 RPM and 3000 N, 64.2 RPM.

On the development of high-frequency torsional impact drilling techniques for hard formation drilling

Stick-slip vibration is a big problem that the drilling of deep wells has to face, especially for drilling of tough formations. This type of vibration leads to failure problems, reduces the rate of penetration, and lowers the borehole quality. Suppression techniques for stick-slip vibration, for example, active control method based on real-time measurement, play important roles in improving the drilling efficiency. The high-frequency torsional impact drilling, however, provides a cheaper and more stable way to mitigate stick-slip in many conditions. This work is aimed to study the high-frequency torsional impact generator, which is used to achieve the function, for this new technique. First, state-of-the-art of high-frequency torsional impact generator is studied by schematically illustrating the existing four structures and their operating principles, followed by comments for these structures. Second, theoretical background of the high-frequency torsional impact drilling is presented, showing how the high-frequency torsional impact generator works to mitigate stick-slip and improve drilling efficiency. Finally, an optimally designed high-frequency torsional impact generator is schematically described. It is an improved version of the assembly of United Diamond and the improvements are based on results of a series of laboratory experiments.