Identification of overpressures resulting from undercompaction and hydrocarbon generation in shale dominated settings using well log data

Based on the concepts of organic geochemistry and well log characteristics, we discuss the differences between undercompaction overpressure (UCOP) and hydro-carbon-generating pressurization (HGP) from well logs in the Chang 7 Shale, Ordos Basin. The results revealed that shales have better hydrocarbon generation potential than mudstones. We found the UCOP is characterized by significant changes of acoustic traveltime (AC), compensation neutron (CNL), density (DEN) and resistivity (RT) on the well logs. Whereas the HGP causes obvious changes in the AC and RT logs, minor deviations are generally revealed in the CNL and DEN logs. Further stud-ies revealed that while UCOP occurs primarily in thick shale layers of the sedimentary center, HGP is predominant in the thin shales of the sedimentary edge. The reason for the above difference may be attributed to the ubiquity of the shales associated with HGP, with the variation in Well logs caused by the HGP concealed by the abnormal variation of UCOP. These findings thus revealed the distribution and well log features of abnormal overpressure for the different generating mechanisms, thus providing significant guidance for further exploration and development of the overpressured formations.

Earnings forecast revisions and securities prices evolution in the Tunisian stock market

Purpose The purpose of this paper is to investigate the effect of forecast earnings’ revision on the evolution of securities prices in the Tunisian stock market. Design/methodology/approach A portfolio study of investor reaction and stock prices following revisions is first conducted to highlight the existence of abnormal return related to analysts’ earnings revisions. Analysis is then supplemented by a second empirical investigation based on the panel data to quantify the effect of revision on the abnormal profitability of securities. Findings The evidence found in this paper validates the fundamental theoretical hypothesis according to which the psychological bias resulting from the effect of the forecast earnings revision is related to the abnormal profitability of the securities. The authors conclude the importance of the revision impact on investors’ behavior on one hand, and the informational content of the analysts’ forecasts and the biases which they lead on the other hand. Originality/value Globally, the empirical illustrations largely validate the findings of behavioral models particularly that of Kormendi and Lippe (1987), Cornell and Letsman (1989), Beaver et al. (2008) which states that investors under psychological bias, react to the effect of forecast earnings revision by an abnormal variation in stock prices.