Geodynamic hazards and risk assessment at the Karachaganak oil,gas,and condensate field

The geodynamic hazards and risk assessment at the Karachaganak oil,gas,and condensate field(KOGCF)were explored on the northern board of the Pre-Caspian Basin to predict the consequences of the longterm exploitation of this field.We integrate multiple measurements,including repeated accurate leveling,Global Positioning System(GPS)measurements,and high precision gravimetric and seismological monitoring at the KOGCF.The results of geodynamic monitoring at the KOGCF for the first time made it possible to prove noticeable seismic deformation processes in the sedimentary cover under the influence of hydrocarbon production.The vertical displacements and horizontal movement along faults,changes in local gravity anomalies,and earthquake sources at depths comparable to hydrocarbon production intervals at the KOGCF have been identified.The maximum amplitudes of modern vertical movement of the earth’s surface and the minimum values of the differently oriented horizontal movement were revealed within the projection on the ground surface of the crest of the carbonate massif(Upper Devonian-Lower Permian age).The results suggest the expansion of uneven compression in the crest of the KOGCF while tension processes occur on its periphery.There is a decrease in gravity variations in relation to the slopes of this massif in areas with active hydrocarbon production.An extended zone of high-gradient steps of AGa anomalies,spatially coinciding with the position of fault zones,is mapped along the periphery of the contour of production wells.In the northeastern part of the KOGCF,seismic events were registered practically in the depth intervals of the productive horizons from which hydrocarbons are produced.A spatial relationship between the seismic events and the anomalous deformation activity in the northeast KOGCF has been revealed.Consequently,the field development has provoked both intense deformation of the earth’s surface and weak local seismicity.

On some problems of seismic crustal phase

In this paper, some practical problems in seismological observations are discussed on the identification of seismiccrustal phase, such as: “whether P (Pg) and S(Sg) are direct waves or not?”; “whether S(Sg) and Lg as well asng and P (Pg) are two kinds of waves or identical wave?”;“on seismoiogicai phases in regional travel-timetable”;“on the symbols and identifications of phases in seismological observation repors”;“on the relation between mLg and ML”, and so on. Some confused ideas on these problems are clarified.