Study on Wellbore Stability of Shallow Sediments in Deepwater Drilling
Method: In this paper, the shallow formation around the borehole is divided into plastic zone and elastic zone considering it under nonuniform in-situ stress. The collapse pressure formula of shallow formation is derived by taking the shrinkage rate of the borehole as the instability criterion. The fracturing pressure calculation model of shallow sediment under non-uniform in-situ stress is derived by combining the theory of excess pore pressure and hydraulic fracturing.
An Empirical Correlation for Compressibility of Shallow Depth Clays in Deepwater Gulf of Mexico
Settlement of subsea structures is an important design consideration, yet it is typically estimated using empirical correlations. A total of 74 consolidation test results from deepwater projects are collected and analyzed to develop an empirical correlation for shallow depth (less than 20 m) deepwater clays in the Gulf of Mexico. Compression indexes with and without clay structural effects are separately considered. Most of the published empirical correlations are irrelevant to offshore clays and the commonly used empirical correlation that uses liquid limit could significantly underestimate the peak compression index of deepwater offshore clays. Initial void ratio is selected as an independent variable for peak compression index estimation. A power function type correlation is proposed between the peak compression index and initial void ratio. With the lower and upper bounds (±30 %), the proposed empirical correlation encompasses the majority of the peak compression index data considering the structural effects. The proposed correlation is applicable for deepwater clays in the Gulf of Mexico having initial void ratios between 1 and 4.Copyright © 2014 by ASME
Time and Heritage
As a historian studying what can be considered a form of intellectual history, I have slowly come to adopt Michel de Certeau’s observation made at the end of the 1980s that ‘objectifying the past, for the last three centuries, has undoubtedly left unconsidered time within a discipline that has continued to use it as a taxonomic instrument’. To a certain degree, time has become commonplace for the historian who has preserved or instrumentalized it. It is not considered because it is inconceivable, but because we do not think of it or, more simply, we do not think about it. As a historian attempting to pay attention to the time I’m living in, I have thus, like many others, noticed the swift development of the category of the present until it has become obvious that the present is omnipresent. This is what I refer to here as ‘presentism’.