Petroleum Drilling Techniques is supervised by China Petrochemical Corporation (Sinopec Group), sponsored by Sinopec Research Institute of Petroleum Engineering.
It aims to serve the authors and readers interested in the field of petroleum, and promote the development of petroleum engineering technology. Its scope covers oil exploitation, oil drilling, and oil drilling equipment.
Petroleum Drilling Techniques is included in CSCD, CA, EBSCO. Impact factor is 1.650.
To investigate the penetration-rate enhancement effect of ultrasonic high-frequency rotary-percussive (UHFRP) drilling compared to conventional rotary drilling and determine the influence of different drilling conditions and parameters on UHFRP rock-breaking efficiency, we designed an ultrasonic vibration pup joint and built a simulation test bench for ultrasonic rock breaking. Using the control variable method and orthogonal experiment method, we carried out tests on the penetration-rate enhancement effect of ultrasonic rock breaking and the corresponding efficiency-influencing factors. Thereby we obtained the influence pattern of weight on bit, ultrasonic amplitude, rotary speed, and drill bit diameter on the UHFRP rock-breaking efficiency. The test results showed that compared with conventional rotary rock breaking, the UHFRP drilling had higher rock-breaking efficiency at normal temperatures and pressures in the laboratory, with an average penetration-rate increase of 77.65%. In addition, weight on bit, ultrasonic amplitude, drill bit diameter, and rotary speed was in descending order in terms of their influence on the rock-breaking efficiency of UHFRP drilling. Furthermore, the influence of weight on bit and ultrasonic amplitude were both highly significant and a larger ultrasonic amplitude resulted in higher rock-breaking efficiency. The results of this research demonstrated that the UHFRP drilling technology provides a new rock-breaking method for penetration-rate enhancement in deep hard formations.
As the existing acoustic logging tools cannot meet the requirements of “look-ahead” detection, the research on “look-ahead” acoustic logging while drilling (LWD) was performed based on the phased array technology. The directional radiation and scanning reception of acoustic energy were realized by the linear-phased-array (LPA) acoustic wave radiator and annular-phased-array (APA) acoustic receiver stations. The responses of monopole and phased-array acoustic logging to a formation interface ahead of the bit are numerically simulated by the finite-difference algorithm. The results showed that the acoustic fields of “look-ahead” acoustic LWD are more complex than those of conventional acoustic reflection logging, because of the wave scattering at the well bottom. The amplitude of P-P echo waves can be significantly enhanced by directionally enhancing the acoustic energy radiated into the formation ahead of the bit with LPA acoustic radiator as compared with the monopole acoustic radiator. In comparison with the monopole acoustic receiver, the APA acoustic receiver station can approximately determine the azimuth of the formation interface ahead of the bit by analyzing the amplitude distribution of P-P echo waves in the scanning reception waveforms. The research results confirmed that detecting geological anomalies ahead of the bit with phased-array acoustic logging is feasible, and it can provide a theoretical basis for the development of industrial prototypes.
Fractures in the Bekhme carbonate reservoir, the main production layer of oilfield A in Iraqi Kurdistan, have caused reductions in the formation pressure over the last few years. As a result, downhole failures such as drilling fluid loss and reservoir pollution are often encountered, which further contribute to low rates of penetration (ROP), low levels of single-well production, high water cuts, etc. We studied and applied a new under-balanced drilling technique of injecting nitrogen into the annular space with crude oil as the drilling fluid. In this technique, the traditional aeration mode was abandoned and nitrogen was injected into the wellbore from the valve at the head side of the casing. Then, it directly flew back to the wellhead along with the drilling fluid in the wellbore. In this process, nitrogen only participated partially in drilling fluid circulation, and the drilling fluid column pressure in the bottom hole was reduced by lowering that in the upper wellbore hole. As a result, under-balanced drilling is achieved without downhole measurement while drilling (MWD) and signal transmission being affected. This technique has been successfully applied to 6 wells in oilfield A without any downhole failures such as lost circulation, well kicks, or wellbore instability. Drilling while producing has also been achieved. Compared with conventional drilling techniques, the technique proposed in this paper enhanced the ROP greatly and increased single-well production by 1 to 3 times. Research and applications demonstrate that this under-balanced drilling technique of nitrogen injection into crude oil enables safe drilling in mature oilfields characterized by low formation pressure and narrow safe density window and ultimately improves oil recovery factor and development efficiency.
To address the deteriorating effect of reacidizing of water injection wells in the Bohai Oilfield, a study on the effect-prolonged acidizing technology for water injection wells was carried out. The effect-prolonged acid was prepared by adding an anti-swelling agent and a surfactant to three kinds of low-concentration deep retarded acid, which were used to work synergistically and enhance the reservoir protection performance of the acid. At 60 °C, the as-prepared acid was tested with respect to its corrosion effect on field scale samples, calcium montmorillonite, and silica, its scale inhibition of injected water, its oil-washing performance, retardation, total corrosion rate, and prolonged effect with dynamic displacements. The results showed that the corrosion rate of the effect-prolonged acid on the calcium montmorillonite and scale samples could reach 45.23% and 86.08% respectively, whereas that on silica was only 0.22%. The acid had a strong scale-inhibiting ability and had a surface tension of 12.77 mN/m. Its corrosion rate on rock powder could reach 9.39%, 13.64%, and 24.54% after 2, 4, and 6 h, respectively. And after dynamic displacements, the increase in the permeability after the injection of water at a volume of 20 times the pore volume remained at 1.8–1.9 times that before acidizing. The proposed technology was applied to 14 wells in the Bohai Oilfield, achieving remarkable results. The results showed that the effect-prolonged acid proposed in this paper performed well in removing blocking, protecting the reservoir framework, retarding the acid–rock reaction, demonstrating a high total corrosion rate, and prolonging the acidizing effect, which makes it worthy of wide application.
The existing conventional bridge slurry plugging materials have problems such as weak fracture adaptability, shallow plugging layers and low success rates of lost circulation control. For this reason, different specifications of elastic mesh materials were selected for evaluation tests of compressive resilience, tensile strength and temperature resistance, and the one with the optimal performance was identified. In addition, we investigated the influence of sizes, shapes and concentrations of the elastic mesh material on the efficacy of lost circulation control. Experimental results indicate that No. 1 elastic mesh material is suitable for lost circulation control, due to its low permanent compressive rate of 10% at 50% of its compressive strength, high tensile strength of 150 kPa and high temperature resistance of 150 °C. The cubic elastic mesh material can remain in fractures and thus presents excellent performance in lost circulation control. The elastic mesh material in the size of 5.0 mm × 5.0 mm × 5.0 mm has the best plugging performance in wedge-shaped fracture in the size of 5.0 mm × 4.0 mm. In addition, the optimal concentration of the elastic mesh material is 0.08%, and the success rate of one-time lost circulation control has reached 86.7% after the elastic mesh material has been applied in multiple wells. The research demonstrated that the elastic mesh material has good adaptability and plugging effect for fractured formations and can solve the problem of lost circulation.
Because the hydration reaction of cement is unable to proceed below the freezing point and hinders cementing, a research on the optimization and enhancement mechanism of hardening properties for early strength of modified alumina cement was conducted. Changes in setting time, fluidity and compressive strength of cement at different temperatures of 0 °C, −10 °C, and −18 °C were compared, and the relationship between these changes at different temperatures and the setting time modifier SCEG was studied. Based on the analysis of phase compositions and microstructures of hydration products, the mechanism of hardening of cement at minus temperature was studied, and gypsum was added to promote the formation of AFt so as to enhance the compressive strength of hardened cement paste. The experiment demonstrated that the cement can be hardened within 0.3–6.0 h when SCEG about 0–3% cement mass is added to the modified alumina cement from 0 °C to −18 °C. In that case, its compressive strength can reach 9.7–11.2 MPa within 24 hours and even rise by 30% after gypsum about 10%–15% cement mass is added. X-ray diffraction (XRD) analysis indicates that the main hydrated mineral in the cement is aluminate clinker instead of silicate clinker at minus temperature, with Ca2 Al(Al,Si)2 O7, AFm, AFt, and a few C–S–H as the main products. To be specific, a higher content of AFt can bring higher compressive strength of hardened cement paste. The results show that modified alumina cement possesses optimized hardening properties at minus temperatures, and appropriate amount of gypsum can increase the content of AFt in hydration products, improving the compressive strength of hardened cement paste.
