A multi-mineral model for predicting petrophysical properties of complex metamorphic reservoirs:Case study of the Bozhong Depression,Bohai Sea

Interpreting reservoir properties through log data and logging responses in complex strata is critical for efficient petroleum exploitation,particularly for metamorphic rocks.However,the unsatisfactory accuracy of such interpretations in complex reservoirs has hindered their widespread application,resulting in severe inconvenience.In this study,we proposed a multi-mineral model based on the least-square method and an optimal principle to interpret the logging responses and petrophysical properties of complex hydrocarbon reservoirs.We began by selecting the main minerals based on a comprehensive analysis of log data,X-ray diffraction,petrographic thin sections and scanning electron microscopy(SEM)for three wells in the Bozhong 19-6 structural zone.In combination of the physical properties of these minerals with logging responses,we constructed the multi-mineral model,which can predict the log curves,petrophysical properties and mineral profile.The predicted and measured log data are evaluated using a weighted average error,which shows that the multi-mineral model has satisfactory prediction performance with errors below 11%in most intervals.Finally,we apply the model to a new well“x”in the Bozhong 19-6 structural zone,and the predicted logging responses match well with measured data with the weighted average error below 11.8%for most intervals.Moreover,the lithology is dominated by plagioclase,K-feldspar,and quartz as shown by the mineral profile,which correlates with the lithology of the Archean metamorphic rocks in this region.It is concluded that the multi-mineral model presented in this study provides reasonable methods for interpreting log data in complex metamorphic hydrocarbon reservoirs and could assist in efficient development in the future.

Three-dimensional lithospheric density distribution of China and surrounding regions

In this paper, we analyze lithospheric density distribution of China and surrounding regions on the basis of 30＇ × 30＇ gravity data and 1°×1 °P-wave velodty data, Firstly, we used the empirical equation be- tween the density and the P-wave velocity difference as the base of the initial model of the Asian lithospheric density. Secondly, we calculated the gravity anomaly, caused by the Moho discontinuity and the sedimentary layer discontinuity, by the Parker formula. Thirdly, the gravity anomaly of the spherical harmonics with 2 40 order for the anomalous body below the lithosphere is calculated based on the model of EGM96. Finally, by using Algebra Reconstruction Techniques （ART）, the inversion of 30＇ ~ 30＇ residual lithospheric Bouguer gravity anomaly caused by the lithosphere yields a rather detailed struc- tural model. The results show that the lithospheric density distribution of China and surrounding regions has a certain connection with the tectonic structure. The density is relatively high in the Philippine Sea plate, Japan Sea, the Indian plate, the Kazakhstan shield and the Western Siberia plain, whereas the Tibetan Plateau has low-density characteristics. The minimum value of density lies in the north of Philippines, in the Taiwan province and in the Ryukyu island arc.

High-Pressure Behavior of Ferromagnesite(Mg_(0.81)Fe_(0.19))CO_(3)by Synchrotron X-Ray Diffraction and Raman Spectroscopy up to 53 GPa

Ferromagnesite(Mg,Fe)CO_(3)with 20 mol%iron is a potential host mineral for carbon transport and storage in the Earth mantle.The high-pressure behavior of synthetic ferromagnesite(Mg_(0.81)Fe_(0.19))CO_(3)up to 53 GPa was investigated by synchrotron X-ray diffraction(XRD)and Raman spectroscopy.The iron bearing carbonate underwent spin transition at around 44–46 GPa accompanied by a volume collapse of 1.8%,which also demonstrated a variation in the dνi/dP slope of the Raman modes.The pressure-volume data was fitted by a third-order Birch-Murnaghan equation of state(BM-EoS)for the high spin phase.The best-fit K_(0)=108(1)GPa and K_(0)'=4.2(1).Combining the dνi/dP and the K_(0),the mode Grüneisen parameters of each vibrational mode(T,L,ν4 andν1)were calculated.The effects of iron concentration on the Mg_(1−x)Fe_(x)CO_(3)system related to high-pressure compressibility and vibrational properties are discussed.These results expand the knowledge of the physical properties of carbonates and provide insights to the potential deep carbon host.