• To demonstrate reservoir properties in a plan view projection with objectives to promote optimal field development.• The maps will be used for well placement, reserves calculation, reservoir performance monitoring.• Mapping is part of reservoir characterization, therefore the results of which very depend on the expert’s working knowledge in applied geologic models
DEPOSITIONAL ENVIRONMENTS AND SEDIMENTARY FACIES
Distinctive and Common Sedimentary Facies AssociationsVertical successions principally identified by lithology, associations and vertical arrangement of sedimentary structures indicative of particular sedimentary depositional environments
CARBONATE DEPOSITIONAL ENVIRONMENTS(DIAGRAM BY R.G. LOUCKS AND C.R. HANDFORD, UNPUBLISHED)
SEQUENCE STRATIGRAPHY CONCEPTS• Sequence stratigraphy highlights the role of allogenic controls on patterns of deposition, as opposed to autogenic controls that operate within depositional environments – Eustasy (sea level) – Subsidence (basin tectonics) – Sediment supply (climate and hinterland tectonics)
• A MAPABLE PORTION OF THE TOTAL RESERVOIR WITHIN WHICH GEOLOGICAL AND PETROPHYSICAL PROPERTIES THAT AFFECT THE FLOW OF FLUIDS ARE CONSISTENT AND PREDICTABLY DIFFERENT FROM THE PROPERTIES OF OTHER RESERVOIR ROCK VOLUME ( mod. EBANK, 1987) – A specific volume of reservoir, may be composed of one or more lithologies and any nonreservoir rock types – Correlative and mappable at the interwell scale – Zonation is recognizable on wireline logs – May be in communication with other flow unit
LEVELS OF RESERVOIRHETEROGENETY (fluviatil rock)
GEOLOGICAL AND PETROPHYSICAL DATA USED TO DEFINE FLOW UNITS Core Pore Petrophysical Gamma Ray Flow Core Lithofacies Plugs Types Data Log Units Capillary φ vs k Pressure 5 4 3 2 1
Schematic Reservoir Layering Profile in a Carbonate Reservoir Flow unitBaffles/barriers SA -97A SA -356 SA -71 SA -344 SA -348 SA -37 SA -251 SA -371 SA -346 3150 3150 3100 3100 3250 3200 3150 3100 3200 3150 3200 3200 3150 3300 3250 3200 3150 3250 3250 3250 3200 3250 3300 3250 3200 3300 3300 3250 3350 3300 3250 3350 3350 From Bastian and others
E• BASED ON : – PRODUCTION TESTINGS the most reliable methods – LOGS (electrical logs combined with FDC & CNL) – PRESSURE SURVEY pressure gradient from RFT – SEISMIC hydrocarbon indications
Fluid Contact Determination with fluid gradient from RFT Oil Gra W die at er nt 0 G ra .36 di en 7 t0 psi .4 depth 33 /ft ps i/f t oil OWCwater RFT depth pressure
CORRELATIONS• “Reservoir Correlation” is part of pre-mapping works of reservoir to locate and trace the lateral distribution, continuity, geometry of reservoirs and it’s flow unit.• Correlation should be carried out based all the available data, a sedimentological and stratigraphic model of the reservoirs.• Some pre-correlation works notes: – Wireline log will be the basic data and will be calibrated and integrated with other data analysis results such as core analysis especially. – Vertical profile analysis of well data should be carried out previously to establish the facies, sequences and sedimentary environment. – Zonation of lithology and flow unit, and also marker inentifications should be geologically sound. – Define the zone top & bottom, zone thickness (gross & net) etc.
Tips for Correlation• Stratigraphic Cross Section is the best demonstration of a correlation results.• The section should show reservoir lateral and vertical facies changes, markers continuity, missing & repetition sections, completion & prod. testing notes, etc.• Good markers can be organic shale, coal/lignite, limestone beds, glauconite, siderite etc. which has good continuity and correspond to the geologic events such as maximum flooding, emmergence etc.• Start the correlation with the whole log section of individual well, make zonation based on electro facies then define all markers and zones of interest. Indicates any missing and repetition section. Then carry out a detail correlation of objective reservoirs.• For reservoir connectivity indication use also fluid contents and contacts, pressure data and production performance data• Prepare a good tabulation (database) of geologic data such as depth of top & bottom of reservoir, net & gross thickness, fault’s depth etc.
Tip for Reservoir Mapping• Prepare a good base-map based on coordinates of wells and seismic shot points (line & BM).• Plot the data accurately then start contouring from the highest positions for structure and refer to seismic maps.• Stucture contour should be stop whenever cross/meet the fault plane. Consider the fault throws and missing/repetition sections for the next blocks contouring.• For isopach maps initiate with facies map construction then followed with isopach contouring.• Understand the contouring principles such as no crossing contour etc.
FAULT ANALYSIS SEALING OR NON SEALING• Can be based on : – Log analysis – Well test data – Pressure build-up analysis – Interference test – Production data – Using radioactive tracer – Core & Rock Cutting – Correlation & Sratigraphic analysis