TY - THES

T1 - The geology of the Lauterbach Gasfield

T2 - Geologic modeling in a complex depozone

AU - Geissler, Martin Andreas

N1 - embargoed until 23-09-2015

PY - 2010

Y1 - 2010

N2 - The Lauterbach Gas Field is located in a wedge top deposition environment resulting in a complex architecture. Therefore, every well drilled delivered new insights and altered the perception of reservoir setting. Thus, the aim of the present master thesis is to build a geologic 3D model that reflects the complexity of the reservoir and fulfils the needs of a dynamic reservoir simulation. A dataset provided by Rohöl-Aufsuchungs AG consisting of 3D seismic data and well data forms the base for this study. The Lauterbach Basin is a piggyback basin that formed on top of the Molasse Imbrications and is located at the border of Salzburg and Upper Austria. The basin has an extension of approximately 5.5 x 3.5 km and is truncated in the south by the Alpine thrust system. Above the base, formed by a regional erosional event, five productive reservoir layers were deposited. Turbiditic sediments were shed into the basin from SSE directions. In some layers a second input direction from E is identifiable. The key elements in basin history are the synsedimentary stress from the underlying moving Molasse Imbrications that led to soft deformation of the sediments and a large number of erosive events that are represented in the sedimentary succession. Well log correlation and seismic interpretation in this setting are challenging, because bed thickness is often not much greater than seismic resolution. As a consequence, top and base of a reservoir layer cannot be mapped separately in seismic. According to synthetic seismograms, the reflectors were chosen to represent the top of the reservoir sections. The base of each reservoir successions was constructed using thickness maps that are based on amplitude variations along the seismic reflectors. Furthermore, pressure data from production tests formed a valuable assist in the identification of reservoir connectivity. To characterize the geology of the Lauterbach Basin, a facies model of the reservoir was built using an object based modeling technique. The definition and distribution of different facies groups within the reservoir is essential for the calculation of hydrocarbon volume in place, which was also carried out. The results showed an excellent fit with independent estimates derived from production pressure data.

AB - The Lauterbach Gas Field is located in a wedge top deposition environment resulting in a complex architecture. Therefore, every well drilled delivered new insights and altered the perception of reservoir setting. Thus, the aim of the present master thesis is to build a geologic 3D model that reflects the complexity of the reservoir and fulfils the needs of a dynamic reservoir simulation. A dataset provided by Rohöl-Aufsuchungs AG consisting of 3D seismic data and well data forms the base for this study. The Lauterbach Basin is a piggyback basin that formed on top of the Molasse Imbrications and is located at the border of Salzburg and Upper Austria. The basin has an extension of approximately 5.5 x 3.5 km and is truncated in the south by the Alpine thrust system. Above the base, formed by a regional erosional event, five productive reservoir layers were deposited. Turbiditic sediments were shed into the basin from SSE directions. In some layers a second input direction from E is identifiable. The key elements in basin history are the synsedimentary stress from the underlying moving Molasse Imbrications that led to soft deformation of the sediments and a large number of erosive events that are represented in the sedimentary succession. Well log correlation and seismic interpretation in this setting are challenging, because bed thickness is often not much greater than seismic resolution. As a consequence, top and base of a reservoir layer cannot be mapped separately in seismic. According to synthetic seismograms, the reflectors were chosen to represent the top of the reservoir sections. The base of each reservoir successions was constructed using thickness maps that are based on amplitude variations along the seismic reflectors. Furthermore, pressure data from production tests formed a valuable assist in the identification of reservoir connectivity. To characterize the geology of the Lauterbach Basin, a facies model of the reservoir was built using an object based modeling technique. The definition and distribution of different facies groups within the reservoir is essential for the calculation of hydrocarbon volume in place, which was also carried out. The results showed an excellent fit with independent estimates derived from production pressure data.

KW - Molasse Basin (Austria)

KW - Piggyback Basin

KW - Turbidites

KW - Geologic modeling

KW - Molassezone (Österreich)

KW - Piggyback Becken

KW - Turbidite

KW - Geolgoische Modellierung

M3 - Master's Thesis

ER -