Chapter 3: TRAP Chapter 3: TRAP 3.2 Classification: 3.2 Classification: four major four major types: types: Structural, Structural, Stratigraphic, Stratigraphic, Hydrodynamic and Hydrodynamic and Combination Combination 3.1 Definitions and Concepts 3.1 Definitions and Concepts 3.1.Definitions and Concepts 3.1.Definitions and Concepts • • A trap is subsurface configuration of reservoir A trap is subsurface configuration of reservoir rock and cap rock or seal that has potential to rock and cap rock or seal that has potential to concentrate petroleum in the pores of a reservoir concentrate petroleum in the pores of a reservoir rock rock • • A trap is a geological feature of a reservoir rock A trap is a geological feature of a reservoir rock that restricts the flow of fluids that restricts the flow of fluids • • A trap can content one or more reservoirs A trap can content one or more reservoirs [...]... barrels of oil or 3. 5 trillion cubic feet of gas (Halbouty et al., 197 0) • The Asmari limestone (Oligocene-Miocene), a reservoir with extensive fracture porosity, provides the main producing reservoir • Some single wells have flowed up to 50 million barrels Figure 13 (Southwest-northeast generalized sections through Asmari oil fields) Figure 13 Anticline related to thrust faults 0 3- Painter Reservoir... zone ( Figure 10, Structural contours on top of Ranger zone, Wilmington field, CA) Notice also the cross-cutting faults Figure 10 • From a southwest-northeast cross section of the Wilmington field, we can see the broad arch of the anticline ( Figure 11, Southwestnortheast cross-section A-Z, Wilmington field) The main reservoir occurs beneath the Pliocene unconformity in Miocene- and Pliocene-age deep-sea... which are due to compression are most likely to be found in or near geosynclinal troughs (mangs) Examples of Compressional Fold Traps • 01-The Wilmington oil field in the Los Angeles basin ( Figure 9 , Oil fields of the Los Angeles basin) is a giant anticlinal trap with ultimate recoverable reserves of about 3 billion barrels of oil Figure 9 • It is approximately 15 kilometers long and nearly 5 kilometers... FAULT UNCONFORMITY ANTICLINAL PINCH-OUT BURIED REEF SAND LENS GRADING Figure 8 BASIC HYDROCARBON TRAPS SUB-SALT SEDIMENT TRUNCATION 3. 2.1 Structural Traps • "A structural trap is one whose upper boundary has been made concave, as viewed from below, by some local deformation, such as folding, or faulting, or both, of the reservoir rock." Fold Traps Fold Traps (Compressional ) • Anticlinal traps which are... some oil fields (e.g Sarir field in Libya), a mat of heavy tar is present at the oil-water contact Degradation of the oil by bottom waters moving beneath the oil-water contact may cause this tar to form Tar mats cause considerable production problems because they prevent water from moving upwards and from displacing the produced oil • Boundaries between oil, gas and water may be sharp ( Figure 4a ,... contacts within a reservoir- sharp contact • Gradational ( Figure 4b , Transitional nature of fluid contacts within a reservoir- gradational contact) An abrupt fluid contact usually indicates a permeable reservoir Gradational contacts usually indicate low permeability reservoirs with high capillary pressure Figure 4 • Directly beneath the hydrocarbons is the zone of bottom water ( Figure 5 , Nomenclature... and Pliocene-age deep-sea sands Figure 11 02-Reservoir in the Zagros mountains • The foothills of the Zagros mountains in Iran contain one of the best-known hydrocarbon provinces with production from compressional anticlines ( Figure 12, Location map, southwest Iran and Persian Gulf) Figure 12 • Individual anticlines are up to 60 kilometers in length and 1 0-1 5 kilometers in width • Sixteen of these... hydrodynamic flow of bottom waters ( Figure 6 , Tilted fluid contact caused by hydrodynamic flow) Figure 6 • There may be one or more separate hydrocarbon pools, each with its own fluid contact, within the geographic limits of an oil or gas field ( Figure 7 , Multiple pools within an oil and gas field) Each individual pool may contain one or more pay zones Figure 7 3. 2.Classification Basically, traps... occur in anticlines above thrust planes, and in reservoirs sealed beneath the thrust • In Wyoming, the Painter Reservoir field is a fairly tight anticline ( Figure 14, Structural contours on top of Nugget sandstone, Painter Reservoir field, Wyoming) beneath a thrust plane, which itself is involved in thrusting along its southeastern border Figure 14 ... usually indicate low permeability reservoirs with high capillary pressure Figure 4 • Directly beneath the hydrocarbons is the zone of bottom water ( Figure 5 , Nomenclature of underlying reservoir waters) • The zone of edge water is adjacent to the reservoir Figure 5 • Fluid contacts in a trap are almost always planar but are by no means always horizontal • Should a tilted fluid contact be present, its . predominately oil-saturated rocks and water-saturated rocks. Similarly, either the gas-water contact, GWC ( Figure 3b , Fluid contacts within a reservoir in a gas-water system), • or the gas-oil contact,. contact, GOC ( Figure 3c , Fluid contacts within a reservoir in a gas-oil-water system) is the lower level of the producible gas. The GWC or GOC marks the interface between predominately gas-saturated. two. The oil- water contact, OWC, is the deepest level of producible oil within an individual reservoir • ( Figure 3a , Fluid contacts within a reservoir in an oil-water system). • It marks