oa Wavelet Consistency Assessment for Quantitative Interpretation - A Case Study from Northeastern Saudi Arabia

An onshore exploration 3D survey located in Northeastern Saudi Arabia and covering an area of<br>approximately 6300 square kilometers was acquired in 2003. There are two existing oil fields with<br>Upper Jurassic, carbonate reservoirs controlled by four-way closures, located within the survey.<br>Current exploration activity, away from these fields, is concentrating on stratigraphic plays involving up<br>-dip truncation of regional trends with the hydrocarbon seals being created by dolomitization and<br>cementation within the reservoir.<br>A multi-well feasibility study confirmed that porosity changes within the reservoir at these seal<br>boundaries could be seen using acoustic impedance inversion. One important question on the use of<br>seismic inversion over this large of an area was the wavelet stability. The inversion software used in<br>the project employed a multi-well, multi-trace approach that allowed for very detailed, thorough and<br>semi-automated procedures for conducting a wavelet study.<br>This paper will present the results from wavelet stability tests including analysis of seismic data only by<br>means of a Markov chain Monte Carlo (MCMC) simulation technique. This is followed by scenarios with<br>different combinations of single and multiple wells and seismic data, with varying number of traces<br>around each well used in the calibration and wavelet extraction. The final wavelet determined in the<br>inversion analysis was then cross-checked among the various techniques. This thorough procedure<br>confirmed that the wavelet was zero phase and SEG negative polarity, and that it was reasonably<br>stable throughout the survey.