Papers by Keyword: HPHT

Abstract: The ambition of the world oil industry is currently directed toward the deepest traps of oil and gas, despite the very high temperatures. The objective of this study is to improve and control a conventional formulation of cement slurry that meets the critical conditions during the cementing of 7" liner on high pressure/high temperature (HPHT) gas well at 5570m depth, located at Hassi Berkine in the southern Algeria. Under the influence of high temperature, the characteristics of the cement slurry changed. We carried out several tests on various samples in order to revise the design by using equivalent substitutions of the additives to obtain a better profile. The use of a new, very powerful, synthetic retarder (SR-31L) instead of liquid, modified sodium lignosulfonate (R-15 L) led us to obtain a significant thickening time but decreased the rheological properties as well as fluid loss and free water. We also provided a gas block by introducing latex-styrene-butadiene with a specific stabilizer (LS-1) in combination with a compatible bonding agent (amorphous silica) in aqueous suspension (BA-58L). The study determined one of the best cement slurry designs practicable on different down-hole applications in HPHT wells.

Abstract: The paper presents the results of the High Pressure and High Temperature (HP-HT) sintering and investigation of Ultra High Temperature Ceramics (UHTC) composites of titanium nitride matrix. The aim of this studies were to determine the influence of additives on the ceramic phase composition, microstructure and selected properties. Three different kind of mixtures were prepared. 8 to 22 wt% B₄C, SiC and Si₃N₄ were added. Composites were sintered under high-pressure high-temperature conditions (HP-HT) using a Bridgman-type apparatus under pressure about 6 GPa. Materials were sintered at the range of 1450 to 1690 ° C, duration of sintering was 60s. The phase composition, microstructure, and the apparent density, Young's modulus, hardness and fracture toughness KIC (HV), using the Vickers indentation method were examined. Sintered titanium nitride with the 22 wt% silicon carbide participation was characterized the best physical and mechanical properties. For this material the relative density is 99%, the Young's modulus 435 GPa, Vickers hardness 18.3 GPa HV1 and fracture toughness 5.5 MPa∙m^1/2.

Abstract: Ternary carbide Ti₃SiC₂ is a good binder to make superhard composites with diamonds or cubic boron nitride. Superhard composites are normally made at high temperature and under high pressure around 5 GPa to avoid the phase transformation of diamonds or cubic boron nitride. This paper researched the synthesis of Ti₃SiC₂ from the powders of Ti, Si, and graphite by a cubic presser under 1 GPa to 4 GPa at 1400°C. The decomposition of Ti₃SiC₂ under 5GPa at 1400°C was also researched. From X-ray diffraction (XRD) and scanning electron microscopy (SEM) results, Ti₃SiC₂ was synthesized in 30 min under 1 GPa at 1400°C. The impurities were TiSi₂, Ti₅Si₃C_x, and TiC. As the pressure increased from 1GPa to 4GPa, less Ti₃SiC₂ more TiSi₂ was synthesized. Therefore, high presser > 1GPa is unfavorable for the synthesis of Ti₃SiC₂. After treated under 5GPa at 1400°C, pure Ti₃SiC₂ was decomposed.

Abstract: Manifestation of friction between the drill string and the borehole is of special importance for modern drilling. A novel lubricity tester, in combination with high pressure high temperature(HPHT) actuators, has been designed to permit the evaluation and testing of various types and the lubricity of drilling fluids by simulating the rotational speed of the drill pipe and pressure exerted against the borehole. This instrument mainly consists of four parts, i.e., a friction mechanism, HPHT actuators, the computational control system, and a load apparatus. The key test cell has been introduced. The lubricity of the typical drilling-in system(PRD) has been evaluated using this instrument. The results showed that except for the filtration, the designed lubricity tester can effectively describe the friction behaviors in the whole dynamic drilling, by rotating the rod in the given environment.

Abstract: In this paper, a new dopant of P₃N₅ (phosphorus nitride) was doped into the diamond growth cell to grow diamond crystals by temperature gradient growth method (TGM) under high pressure and high temperature (HPHT). The experiments were performed at a fixed pressure of about 6.0 GPa and temperatures of 1600-1650 K. The gained diamond crystals were characterized by infrared (IR) absorption spectroscopy, micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. IR measurements demonstrated that, nitrogen atom was indeed doped into diamond crystals, and the diamond crystals with perfect shape containing nitrogen concentration ranging from 461 atomic parts per million (ppm) to 2186 atomic ppm were successfully synthesized. Nitrogen atoms present in diamond crystal were predominantly in isolated form accompanied by a small amount of nitrogen pairs. Micro-Raman spectra implied that crystalline quality deteriorated with nitrogen concentration gradually increased in diamond-growing environment. The XPS spectra revealed that only a few of phosphorus impurities about tens of ppm level were incorporated into a diamond crystal which was heavily doped with P₃N₅. This study will promote the application of doping diamonds in micro-electronics field and other fields.

Abstract: In this study we report on the synthesis and characterization of thermally stable polycrystalline diamond (PCD) using Ni-based alloys catalyst as a sintering aid and the B-doped diamond powder in the infiltrating way. The samples were treated at 5.6 GPa and 1200–1480 °C for 10 min in China-type cubic high pressure apparatus. Scanning electron microscopy showed significant intergrowth of the diamond particles sintered in the presence of Ni-based alloy. X-ray diffraction showed the phase change of the samples sintered at the different temperature. Differential thermal analysis (DTA) and thermogravimetric analysis (TG) showed the sample was significantly more heat-resisting compared to conventional PCD. The results showed that the appropriate conditions of thermally stable PCD sintered were 5.6GPa and 1200–1480 °C.

Abstract: The high pressure and temperature, synthesis of diamond from carbonaceous materials, is a complex process highly dependent on variables such as the catalyst/solvent, the crystalline structure of the precursor material, the processing conditions and the type of compressive chamber. The optimum susceptible precursors to be transformed into diamond are those possessing the perfect hexagonal graphite structure, which is the thermodynamically most stable form of carbon at atmospheric pressure and ambient temperature. However, the majority of both industrial and natural graphites, presents a mixture of different atomic structural arrangements that greatly influence the process of diamond synthesis. In this works the influence of rhombohedral and hexagonal phases existing in the graphite was performed by means of a software refinement of the crystal structures using the Rietveld method. The thermobaric treatment, which determine the structural parameters, was conducted in a high pressure anvil type device with a central concavity. All experiments were carried out at 1200°C and pressures varying from 4.3 to 5.0 GPa. It was determined that the degree of graphite to diamond transformation is directly associated with the content of rhombohedral phase.

Abstract: The development of technological processes for obtaining small size diamond powder is of industrial interest as basic products for roughing and finishing surfaces, like in the polishing of ornamental rocks. Therefore, this work investigates the influence of zinc, as a doping agent, in association with the graphite to diamond transformation, which occurs during high pressure and high temperature synthesis in the presence of Ni-Mn as a catalyst-solvent metallic alloy. Diamond synthesis was carried out at 4.7 GPa of pressure and 1300°C using a reactive mixture with 1:1 ratio of graphite and Ni-Mn alloy powders doped with up to 6% of Zn. The results indicated that the highest diamond yield was obtained for 0.5% while the lowest yield for 6% of Zn. Regardless the Zn content , the diamond crystal were produced with 212/150 μm of granulometry.

Abstract: Ti₃SiC₂, a ternary carbide, was proposed at this paper to use as the binder of polycrystalline diamonds to overcome the weaknesses of traditional metal binders and ceramic binders. Ti₃SiC₂ was first reported to be in-situ synthesized under high pressure (4GPa) and at high temperature (1400°C) (HPHT) from the mixtures of Ti, Si and graphite powders or the mixture of Ti, SiC and graphite powders. Ti₃SiC₂-damond composites were also made at HPHT from the previous mixtures and diamond particles. TiC_x, Ti₅Si₃C_x and TiSi₂ were main impurities and/or intermediate products of Ti₃SiC₂ samples synthesized at HPHT. Ti₃SiC₂ content increased as synthesized time increased from 10 min to 60 min. For as-synthesized composites, diamond particles were evenly distributed in matrix. The diamond particles are bonded well with the matrix by three types of interface.

Abstract: Polycrystalline filled Skutterudite compounds Ba_xCo₄Sb₁₂ (0-x-0.5) are synthesized by high pressure and high temperature （HPHT） technique. The thermal conductivity for CoSb₃ is depressed significantly by Ba-filling combined HPHT technique. The value of 1.25 Wm^-1 K^-1 for Ba_0.372Co₄Sb₁₂ is obtained at 633K. The dimensionless thermoelectric figure of merit ZT, increases with temperature increasing and reaches a maximal value of 1.01 at 663 K.