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.
Instituting a multilateral-well enhanced geothermal system is a novel method to enhance fluid injectivity and productivity for geothermal development by using lateral wells. To study the influencing laws of different factors of the system on injection-production performance, fluid flow and heat transfer experiments for multilateral wells were conducted. Experiments were performed to evaluate the injection-production performance and investigate the effects of different factors on the injectivity and productivity of lateral wells based on the multilateral-well enhanced geothermal experimental system and artificial rock samples. In addition, the injection-production performances of a multilateral well and a single vertical well were compared. Results indicated that decreasing the injection temperature can increase injection pressure and improve the injectivity of the system, while increasing the number and length of lateral wells can decrease the injection pressure and increase the outlet flow rate. The injection-production performance of the multilateral-well enhanced geothermal system is much better than that of the single-vertical-well geothermal system and is more suitable for the development and injection of geothermal energy. Findings prove that multilateral wells can enhance the injectivity and productivity of the geothermal system, providing a theoretical foundation and guidance for field applications of the multilateral-well enhanced geothermal system.
An AICD screen with a by-pass sliding sleeve was designed and matching technologies were improved to fulfill the dual demands of water and sand control and to solve the problems in gravel packing with water control screen and implementing subsequent formation treatment. A sand control technique using gravel packing combined with water control for horizontal wells was then proposed. The sliding sleeve can provide an additional flow channel to decrease the packing pressure and can be opened or closed on demand to complete formation treatments and enhance fluid production. To confirm the feasibility of the technique, we designed a visual simulation test platform for gravel packing in horizontal wells. The platform can collect pressure and flow rate data, record the gravel packing in real time, quantitatively analyze and visually evaluate gravel packing with water control for the optimization of construction parameters. Comparative tests of a conventional AICD screen and an AICD screen with a by-pass sliding sleeve were carried out. The results showed that gravel packing efficiency of the AICD screen with a by-pass sliding sleeve can reach 100% with a flow rate of 0.4 m3/min and a sand concentration of 4%. Compared with the conventional one, the novel screen led to lower packing pressure, shorter working time, and more compact gravel packing. In addition, the sliding sleeve also showed good switching performance after the tests. The research confirmed that the structure of the AICD screen with a by-pass sliding sleeve is reasonably designed and the matching water control packing technique is feasible and can provide horizontal wells with a new solution to sand control completion with water control.
In order to prevent the drilling fluid filtrate from entering the formation, to maintain the wellbore stability, and to protect the reservoir, a procedure to activate a graphene surface was conducted by using a modified Hummers method. It introduced carboxyl, hydroxyl, epoxy groups, and other active groups, resulting in a kind of graphene-modified film-forming agent SMSL with ultra-low permeability. It was prepared by grafting copolymerization with selected monomers on the surface of active graphene. The molecular structure, micromorphology, and dispersive state of SMSL were analyzed by the infrared spectrometer, the element analyzer, the atomic force microscope, and the synchronous thermal analyzer. Researchers used pressure transfer tests, core self-seepage tests, and SEM to evaluate the dense film-forming plugging characteristics of SMSL and the compatibility of SMSL with the water-based drilling fluid. The results showed that the molecular structure of SMSL met the design requirements, and it could significantly reduce the pressure transfer and self-seepage effect of rocks. Specifically, the shale film-forming efficiency was 162.96% higher than that of the conventional polymer film-forming agent, and the self-seepage capacity of tight sandstone was decreased by 88.74%, with very good compatibility with the water-based drilling fluid. The research indicated that when SMSL was added into the drilling fluid, a dense film can form on the wellbore to prevent the filtrate from entering the formation and thus can maintain wellbore stability and protect the reservoir.
Borehole collapse, lost circulation, and sticking frequently happen in deep formations when drilling in the western Sichuan Basin. When drilling with oil-based drilling fluids, it is difficult for a thick filter cake to form. In addition, the low density of the filter cake leads to high pressure penetration ability at the borehole. To solve this problem, based on the mechanism of drilling fluid film forming, a borehole protection agent with the compact film, CQ-NFF, was synthesized from styrene, acrylate, and other raw materials using the core-shell structural design, which is suitable for the middle layer with a temperature no more than 150 °C in deep well drilling in the area. According to the analysis results of the geological characteristics and engineering characteristics of high-risk formations and the d90 rule, an inner-filling plugging agent was formed from ultra-fine calcium carbonate, elastic graphite, high strength resin, and highly dispersed fiber. The film-forming mechanism and morphology of drilling fluid were analyzed by scanning electron microscope (SEM). Film forming effects were evaluated in filtration tests at high temperature and high pressure along with water and oil loss tests during drilling penetration at high temperature. By means of the sand bed filtration experiments at high temperature and high pressure, the plugging capacity of the filling material was evaluated. Experimental results show that CQ-NFF can form a compact film in water-in-oil emulsion and oil-based drilling fluid, and the film can be adsorbed on the surface of the filter cake effectively. The pressure resisting and plugging capacity of the film can reach 2.0 MPa. After the inner-filling plugging agent was added to the oil-based drilling fluid, the pressure resisting capacity of the inner filter cake was increased to over 3.5 MPa. The wellbore strengthening technology with oil-based drilling fluid, treating chemicals as the core, was applied in Well Shuangtan 6 and Well Zhongjiang 2. The results showed a remarkable application effect that the downhole downtime due to lost circulation in deep formations, borehole collapse, or drill pipe sticking, was greatly reduced.
Focusing on such problems as poor high-temperature stability of drilling fluids and downhole instruments in the development of deep gas and oil, phase change materials were introduced into drilling fluids for the first time to model the cooling of drilling fluids in deep wells based on phase change heat storage principle. First, the heat storage characteristics of the phase change materials were investigated on the basis of evaluating the thermophysical properties of the phase change materials. Then, the influence of phase change materials on the rheological and filtration properties of drilling fluids was comparatively evaluated. Finally, the experimental curves for the cooling performance of drilling fluids were measured using a self-made experimental device of drilling fluid circulating simulation. The results showed that the phase change temperature and the latent heat of phase change for the phase change materials 1#–3# were approximately 120–145 °C and 90.3–280.6 J/g, respectively; the phase change material 2# displayed the highest latent heat and the best heat storage performance of the phase change, exhibiting compatibility with drilling fluid. Specifically, the viscosity, shear force, and filtration of the drilling fluids were basically unchanged when the concentration of the phase change material 2# increased to 12%, and the circulating temperature of the drilling fluids could be reduced by about 20 °C, correspondingly. In addition, the phase change material 2# exhibited excellent reuse properties. In conclusion, the circulating temperature of the drilling fluids could be reduced by referring to the principle of phase change heat storage of phase change materials, which could provide new technical thinking to apply to cooling technologies for high-temperature drilling fluids in deep wells.
Technical difficulties such as low ROP, long drilling cycle, poor cementing quality, and high drilling safety risk occur when drilling the upper part of complex ultra-deep wells in the Bozi 1 Block of the Kelasu structure. To break down these problems, a casing program was optimized in terms of regional geological characteristics and theoretical analysis; a series of technologies in ROP enhancement were optimized; a combined evaporite bed determining technology was proposed, and a series of antileaking and lost circulation control technical measures and cementing measures were formulated. Consequently, key technologies for drilling and completion of complex ultra-deep wells in Bozi 1 Block of Kelasu structure were formed. The technologies had been tested in four wells including B1103 with excellent potential for universal applicability. Compared with the neighboring wells using other drilling and completion technologies, there were many positive advances. For example, the ROP was increased by 34.4%, the drilling cycle was reduced by 131 days, and the completion cycle was cut by 141 days. This showed that the technologies could solve the technical difficulties in drilling and completing ultra-deep wells in the Bozi 1 Block, thus ensuring safe and efficient drilling and completion. Hence, the key technologies could be widely adopted in this block.
