The velocity anisotropy parameters and elastic constants play a very important role to estimate Young's modulus and Poisson's ratios accurately. For geomechanics applications such as hydraulic fracturing design, analysis of wellbore stability and rock failure, determination of in situ stress and assessment of the response of reservoirs and surrounding rocks to changes in pore pressure and stress, Young's modulus and Poisson's ratios play a very important role. Four rock samples were collected from four different wells situated in study area. The ultrasonic transmission method has been used to measure P-wave, Sh-wave and Sv-wave travel times as a function of orientation and confining pressure. The five independent stiffnesses constants, Young's moduli, Poisson's ratios and Bulk moduli of the samples were estimated. The Poisson's ratios ( 12 13 , ϑ ϑ and 31 ϑ ) are varying as the confining pressure is changed. The axial strain is larger than the lateral strain, resulting 31 12 ϑ ϑ < . For shales, the Young's modulus measured parallel to bedding E 1 is usually greater than the Young's modulus measured perpendicular to bedding E 3 . Through this study it has been observed that, there is a strong effect of anisotropy parameters on Young's modulus and Poisson's ratio.

The Tripura state went through extensive geological tectonics that resulted in the creation of complex structural styles with different fault types, lineaments, and plate boundaries, which in turn caused possible zones with over-pressured formations characterized by higher seismic amplitude signatures. Without accurate estimates of pore pressures, drilling through these hazardous zones is very troublesome and could jeopardize the whole drilling rig site. Pore pressures are easily predicted for sediments with normal pressure gradient. The prediction of pore pressure for the abnormally pressured (i.e., overpressured) sediments is more difficult and more important. Understanding of the pore pressure is a requirement of the drilling plan in order to design a proper casing program. With balanced drilling mud, overpressured formations, and borehole instability will be effectively controlled while drilling and completing the well. Well control events such as formation fluid kicks, loss of mud circulation, surface blowouts, and subsurface kicks can be avoided with the use of accurate pore pressure and fracture gradient predictions in the design process. In this study, transform models using modified Eaton's method were used to predict pore pressures from seismic interval velocities. Corrected two-way travel times and average velocity values for 28 sorted common depth points were input into the transform for pore pressures prediction predicted pore pressures show a reasonable match when plotted against formation pressure data from the offset wells namely AD-4 trend, Agartala Dome-6. Ambasa trend, Kathalchari trend, Kubal, Masimpur-3, Rokhia structure-RO1, and Tichna structure-TI1. In this study, it is observed that overpressure starts at shallow depths (1,482-2,145 m) in synclinal section while in flank section it starts deeper (2,653-5,919 m) in Atharamura anticline. It is also observed that the most of wells showing pressure match are located in the western side of the Atharamura. The maximum predicted pore pressure gradient observed in this study is 1.03 psi/feet in both synclinal and flank sections of Atharamura anticline. Based on our observations, it is interpreted that Tripura region is characterized by single pressure source and the pressure is distributed evenly in all the anticlines in this region.

The Tulamura anticline falls in the state Tripura, Northeast India. The anticline is extended up to neighbour country Bangladesh. The region is characterized by huge anticlines, normal faults and abnormally pressured formations which causes a wide margin of uncertainties in wildcat well planning and design. These geological complexities of Tulamura anticline make the drilling engineers more challenging. Therefore, a proper well design is essential in such a region to prevent blowout. Drilling engineer requires to maintain wellbore pressure between the pore pressure and fracture pressure to reduce the possibility of a kick and a formation damage. Pore pressure plays an important role to design a safe and economical well in such a high pressure and temperature reservoir. For wildcat drilling, only seismic data are available in the study area. There are various methods to predict pore pressure from seismic velocity data. Modified Eaton's method is widely used for the pore pressure prediction from seismic data in terms of the velocity ratio. Modified Eaton's equations may cause an error by manual selection of compaction trend line which is used to find normal compaction velocity. The main objectives of this study are to develop a new method to predict pore pressure and safe well design on the top of Tulamura anticline in terms of pore pressure. The new method is validated by a well-known method, modified Eaton's method, and RFT pressure data from offset wells. An excellent match with pore pressures estimated from RFT pressure data and predicted by new model along with modified Eaton's method is observed in this research work. The efficiency and accuracy level of the hybrid model is more as compared to other methods as it does not require compaction velocity data; thus, an error caused by manual compaction trend can be eliminated. Pore pressure predicted by new method indicates result up to the 6000 m, which is up to the basement rock. The predicted pore pressures by new method are used as an input to calculate the fracture pressure by Hubbert and Willis method, Mathews and Killy method and modified Eaton's method. Equivalent mud weight selection is carried out using median line principle with additional 0.3 ppg, 0.3 ppg and 0.2 ppg of swab pressure, surge pressure and safety factor, respectively, for calculation of all casing pipes. Casing setting depths are selected based on pore pressure gradient, fracture pressure gradient and mud weight using graphical method. Here, four types of casing setting depths are selected: conductor, surface, intermediate and production casings at 100 ft, 6050 ft, 15500 ft and 18,500 ft, respectively, by new methods, but the casing setting depths for intermediate are at 13500 ft in the case of modified Eaton's method. The casing policy is selected based on burst pressure, collapse pressure and tension load. For each casing, kick tolerance in bbl is determined from kick tolerance graph to prevent the blowout. Finally, comparative safe and economical wells are designed on the top of Tulamu...

The main objective of the paper is to estimate seismic wave attenuation from the decay rate of coda wave amplitudes of digital seismogram of local earthquakes (epicentral distance < 100 km) following statistical approach. Three earthquake events have been selected for estimation of coda wave attenuation quality factor (Q c ). The coda wave of 9 seismograms from 3 local earthquakes recorded digitally by three seismic stations in the region have been analyzed for this purpose at ten central frequencies (1, 1.5,2,3,4,6,8,12, 16 and 18Hz) and three lapse time windows of 20, 30 and 40 seconds duration. Single backscattering model proposed by Aki (1969) and extended by Aki and Chouet (1975) and Sato

The discovery of gravitational waves and black holes has started a new era of gravitational wave astronomy that allows us to probe the underpinning features of gravity and astrophysics in extreme environments of the universe. In this article, we investigate one such study with an extreme mass-ratio inspiral system where the primary object is a spherically symmetric static black hole immersed in a dark matter halo governed by the Hernquist density distribution. We consider the eccentric equatorial orbital motion of the steller-mass object orbiting around the primary and compute measurable effects. We examine the behaviour of dark matter mass and halo radius in generated gravitational wave fluxes and the evolution of eccentric orbital parameters-eccentricity and semi-latus rectum. We further provide an estimate of gravitational wave dephasing and find the seminal role of low-frequency detectors in the observational prospects of such an astrophysical environment.