Online Journal for E&P Geoscientists

Tan, Wenbin ^*1; Tang, David Z.¹; Meyer, Frantz ²; Lawrence, Paul ¹; Bakhiet, AbdelFattah ¹
(1) Exploration Resource Assessment, Saudi Aramco, Dhahran, Saudi Arabia. (2) Carbonate Research Consulting, Conifer, CO.

Well-log signature correlation coupled with core sedimentology is a common practice for resolving stratigraphic frameworks and sequence architectures. Due to the limited availability of the Jurassic cores, well log signatures are usually not sufficiently calibrated with depositional cycles, facies and stratigraphic boundaries (especially when dealing with large stratigraphic intervals), which can cause uncertainties in reconstruction of regional sequence stratigraphic architectures. Seismic stratigraphic interpretation can provide a coarse-scale stratigraphic skeleton; yet it needs to be refined with depositional cycles, facies, and reservoir qualities in order to define subtle stratigraphic traps. By integrating drill cutting sedimentology, electrofacies (rock types), well log correlation, and seismic interpretation, we can reconstruct internal sequence stratigraphic architecture with high confidence.

Drill cutting sedimentology provides continuous details of vertical changes in lithology, depositional facies, cycle stacking patterns, reservoir qualities and diagenesis. Rock types and electrofacies derived from petrophysical analysis across the entire Upper Jurassic stratigraphic interval have been validated using drill cutting sedimentology work. Gamma Ray (GR) log curves are smoothed and displayed in logarithmic format, to enhance the recognition of cycle patterns, as well as make the correlation of well log signatures with depositional cycles more visible. Key seismic reflectors have been found to tie better with smoothed GR log signatures. Fully integrated data from drill cutting sedimentology, electrofacies, well log signature correlation, and seismic interpretation ensured a confident reconstruction of cycles, sequence boundaries, and internal sequence stratigraphic architectures.

This integrated approach was first employed to resolve the regional sequence stratigraphic framework of the Upper Jurassic, which includes multiple source rocks, reservoirs and seals. The newly reconstructed internal sequence stratigraphic architectures have provided additional insights for the exploration of potential stratigraphic traps.