--> Best Practices in Deepwater Exploration Projects: From Stratigraphy to Seismic Interpretation To Prediction Of Reservoirs And Prospect Risking.

AAPG Asia Pacific Region, The 4th AAPG/EAGE/MGS Myanmar Oil and Gas Conference:
Myanmar: A Global Oil and Gas Hotspot: Unleashing the Petroleum Systems Potential

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Best Practices in Deepwater Exploration Projects: From Stratigraphy to Seismic Interpretation To Prediction Of Reservoirs And Prospect Risking.


Exploration of deep-water targets in passive margins is one the best examples to which integration of datasets at different scales provides, a better control on volumetric, risk assessment and prospect ranking. Discovery of hydrocarbon-bearing turbidite sandstones can be considered as a real exploration success, only if, good to excellent reservoir characteristics are proven to ensure deliverability of large volumes during production. Reservoir quality and performance is a critical risk for deep-water exploration projects. The understanding of depositional processes, architecture of the reservoirs relies on integration of the entire dataset including up scaling with iterations between steps. Structural evolution of the rift margins and its thermal evolution, control the maturity of the sediments dumped into the basin. Uplift of rift shoulder mainly related to thermal history and upper mantle architecture, controls the relief of the hinterland and the size of the drainage area. Unfortunately, restoration of the original configuration at time of rift initiation and the following stages till present day is not an easy task. Wells drilled onshore and on the shelf, provide calibration points for the stratigraphy is commonly incomplete and interrupted by stacked hiatus surfaces, as the shelf has been submitted to a series of uplifts and related erosions leading to these major unconformities. Combining biostratigraphical breakdowns and stacking pattern analysis of well data and neighboring outcrops support identification of time hiatuses and better constrain the prediction of sand-prone cycles, so-called predictive stratigraphy. Mapping these unconformities towards the basin is quite essential, as most sand-rich sections of economic interest have been deposited over these sequence boundaries leading to aggradation of thick low stand packages in the case of siliciclastic systems, on the slope, base of slope and basin plain. Large 3D seismic volumes provide an incredible source of data to image the subsurface. Direct calibration of the stratigraphy is not always possible to achieve due to the lack of wells in the basin in case of frontier areas. Nevertheless, interpreting various seismic cubes: PSTM, PSDM, full stack, angle stacks for instance, and computing a whole suite of seismic attributes can partly compensate for the lack, and direct calibration of the acoustic and elastic responses of the various lithologies. Extended elastic impedance inversion (EEI) can be applied to the seismic data to predict lithology and estimate the type of fluids in clastic reservoirs as sand and shale responses, which can be statistically estimated even in the absence of hard data from well logs. Iterative comparisons of the set of structural maps and seismic attribute maps produced by the interpreter team will lead to the prediction and delineation of sand-prone architectural elements such as channels, sheets and lobes, although detailed heterogeneity within the reservoir is normally not accessible from the 3D cubes due to burial and signal attenuation limiting seismic resolution. Study of offset wells and analogues from databases and the field outcrops for input parameters in computation of volumetric and geological risking are highly recommended. The talk includes a series of exploration examples from deep water basins across geographical areas on the aspects of high grading prospects based on predictive stratigraphy, reservoir quality and performance analysis.