Pre-Drilling Prediction Techniques on the High-Temperature High-Pressure Hydrocarbon Reservoirs Offshore Hainan Island,China

Decreasing the risks and geohazards associated with drilling engineering in high-temperature high-pressure(HTHP) geologic settings begins with the implementation of pre-drilling prediction techniques(PPTs). To improve the accuracy of geopressure prediction in HTHP hydrocarbon reservoirs offshore Hainan Island, we made a comprehensive summary of current PPTs to identify existing problems and challenges by analyzing the global distribution of HTHP hydrocarbon reservoirs, the research status of PPTs, and the geologic setting and its HTHP formation mechanism. Our research results indicate that the HTHP formation mechanism in the study area is caused by multiple factors, including rapid loading, diapir intrusions, hydrocarbon generation, and the thermal expansion of pore fluids. Due to this multi-factor interaction, a cloud of HTHP hydrocarbon reservoirs has developed in the Ying-Qiong Basin, but only traditional PPTs have been implemented, based on the assumption of conditions that do not conform to the actual geologic environment, e.g., Bellotti's law and Eaton's law. In this paper, we focus on these issues, identify some challenges and solutions, and call for further PPT research to address the drawbacks of previous works and meet the challenges associated with the deepwater technology gap. In this way, we hope to contribute to the improved accuracy of geopressure prediction prior to drilling and provide support for future HTHP drilling offshore Hainan Island.

Lanthanum-doped Bi_4Ti_3O_(12) ceramics prepared by high-pressure technique

We present an effective way in this paper to increase the density of lanthanum doped bismuth titanate ceramics, Bi4-xLaxTi3O12 （BLT）, thereby significantly improving the performance of the BLT ceramics. Dense BLT ceramicses, Bi4-xLaxTi3O12 （x = 0.25, 0.5, 0.75, 1.0）, are prepared by using nanocrystalline powders fabricated by a -gel method and high-pressure technique. The microstructures of the BLT ceramicses prepared separately by conventional-pressure and high-pressure techniques are investigated by using x-ray diffraction and transmission electron microscope. The influence of La-doping on the densification of bismuth titanate ceramics is investigated. The experimental results indicate that the phase compositions of all samples with various lanthanum dopings sintered at 900℃ possess layer- structure of Bi4Ti3O12. The green compacts are pressed under 2.5 GPa, 3.0 GPa, 3.5 GPa and 4.0 GPa, separately. It is found that the density of BLT ceramics is significantly increased due to the decreasing of porosity in the green compacts by high-pressure process.

Pressure-induced color change arising from transformation between intra-and inter-band transitions in LuH_(2±x)N_(y)

The pressure-induced color change in the nitrogen-doped lutetium hydride has triggered extensive discussions about the underlying physics and potential applications.Here,we study the optical response of LuH_(2±x)N_(y)in a broad frequency range at ambient pressure and its evolution with pressure in the visible spectral range.The broad-band optical spectra at ambient pressure reveal a Drude component associated with intra-band electronic transitions and two Lorentz components(L1 and L2)arising from inter-band electronic transitions.The application of pressure causes a spectral weight transfer from L1 to the Drude component,leading to a blue shift of the plasma edge in the reflectivity spectrum alongside a reduction of the high-frequency reflectivity.Our results suggest that the pressure-induced color change in LuH_(2±x)N_(y)is closely related to the transformation between intra-and inter-band electronic transitions,providing new insights into the mechanism of the pressure-induced color change in LuH_(2±x)N_(y).

Pressure induced color change and evolution of metallic behavior in nitrogen-doped lutetium hydride

By applying pressures up to 42 GPa on the nitrogen-doped lutetium hydride(LuH2_(±x)N_(y)),we have found a gradual change of color from dark-blue to pink-violet in the pressure region of about 12 to 21 GPa.The temperature dependence of resistivity under pressures up to 50.5 GPa shows progressively optimized metallic behavior with pressure.Interestingly,in the pressure region for the color change,a clear decrease of resistivity is observed with the increase of pressure,which is accompanied by a clear increase of the residual resistivity ratio(RRR).Fitting to the low temperature resistivity gives exponents of about 2,suggesting a Fermi-liquid behavior in the low temperature region.The general behavior in a wide temperature region suggests that the electron-phonon scattering is still the dominant one.The magnetoresistance up to 9 T in the state under a pressure of 50.5 GPa shows an almost negligible effect,which suggests that the electric conduction in the pink-violet state is dominated by a single band.It is highly desired to have theoretical efforts in understanding the evolution of color and resistivity in this interesting system.

Preparation and characterization of dense lanthanum-doped bismuth titanate ceramics

In this work, we present an effective way to increase the density of lanthanum-doped bismuth titanate ceramics （Bi4_xLaxTi3Oa2; BLT）. Dense BLT ceramics with formula Bi4LaxTi3012 （when x = 0.25, 0.5, 0.75, 1.0） are prepared by using nanocrystalline powders fabricated by the sol-gel method and high-pressure technique. The thermal decomposition and phase transformation process of the gel precursors are studied by using DTA, infrared spectroscopy （IRS） and X-ray diffraction （XRD）. The micro- structures of BLT ceramics are investigated by using transmission electron microscopy （TEM） and scanning electron microscopy （SEM）. The experimental results indicate that the phase compositions of all samples with various La substitutes at 900℃possess the layer-structure of Bi4Ti3012 （BTO）. The green pellets are pressed under 2.5, 3.0, 3.5 and 4.0 GPa, separately. It is found that the density of BLT ceramics is significantly increased due to the decreasing of porosity in the green compacts by the high-pressure process. The samples are sintered at temperatures between 900 and 1100℃and it is found that the optimum sin- tering temperature is 1100℃. Dense BLT ceramics with 90% of their theoretic density have been achieved from the sample prepared at a sintering temperature of 1100℃ for 1.5 h.