Sweet Spot Determination for Shale Gas Plays, a Multidisciplinary Approach - A Netherlands Case Study
Zijp, Mart *1; Van Bergen, Frank 1; Verreussel, Roel 1; Schavemaker, Yvonne 1; Nelskamp, Susanne 1; Ogg, Willemijn 1; Horikx, Maurits 1
(1) Geological Survey of the Netherlands, TNO Energy, Utrecht, Netherlands.
A revolution is taking place on the worldwide gas market, primarily due to the increase in U.S. natural gas production from shale gas plays. Whereas shale gas is mainstream production in the USA, its exploration and production is still considered ‘unconventional’ elsewhere. Oil and gas regimes in other parts of the world are distinctively different, in terms of geology, regulations, and surface conditions. Developing shale gas plays outside North America therefore remains challenging and will ¬depend on tomorrow’s innovations. It seems unlikely that shale gas production will follow a similar development as seen in the U.S.A. For example, developments in drilling techniques allow for a significant reduction in well pads and thereby surface use. However, this will limit the availability of well information during the exploration stage and therefore accentuates the importance of vintage well data at the onset of developments.
A multi-disciplinary approach is presented for the evaluation of shale gas potential in the sedimentary record by integrating well logs, 3D-seismic data, core descriptions, biofacies analysis, maturity measurements, basin modeling, total organic carbon determination, and mineralogy composition.
A case study from the onshore Netherlands demonstrates the added value of such an approach. Potential pay-zones within drilled sedimentary sections could be identified and correlated between wells, conforming the continuity of these pay zones to provide better GIP estimates. Facies and depositional environment could be derived from micro- and macro-fossils, that could explain some of the differences in mineralogical composition of the rock. Further, combining the information from mudlogs with basin modeling provided insight in the sourcing and presence of gas in the formations. Geomechanical properties could be derived from well log responses and correlated to the mineralogical composition of the rock. Rock strength is, together with the local stress field, key for the success of hydraulic fracturing that will be essential in the development of shale gas.
The multi-disciplinary approach applied to potential shale gas formations in the Dutch subsurface indicated that much can be gained by integrating several data types and sources, especially in basins lacking dedicated exploration wells for shale gas. This includes the Middle East with its high potential for shale gas and its extensive set of data from conventional oil and gas production.
AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain