Geol 404 1st Edition Lecture 23Outline of Last Lecture I. Decision MakingII. Distribution of Prospect ReservoirsIII. Three Point MethodIV. Log NormalityV. Depth Structure MapOutline of Current Lecture VI. MorphologyVII. System TractsVIII. Oil/Gas FieldsIX. Tengiz FieldCurrent LectureVI. Morphologya. Platforms may occur on the continental shelf from the shoreline to the edge of the shelf. They may cover large portions of epeiric seas. b. Carbonate depositional environments can be divided into 5 main settings:- i. Carbonate Ramp: gently sloping, with water depth gradually increasing (~1° Slope). ii. Epeiric platform: similar to ramp. iii. Rimmed shelves: Reef or carbonate bank on outer margin. iv. Isolated platform: Shallow water sedimentation surrounded by deep water. v. Drowned platform: relative sea level rise, and carbonate production can’t keep up. Transition to deep water sedimentation.c. Example of Isolated Platform Bahama Banki. Distribution of faciesdependant on prevailing wind. ii. No terrigenous input at all. iii. Shows the distribution of major Lithofaciesd. Example of Isolated Platform Caicos i. Reef deposition of the Caicos Platform on the leeward margin is controlled by strong easterly trade winds ii. Destruction of the reefs by major storm activity creates skeletal sands which are then converted into oolitic sands by persistent wind-wave agitation.VII. System TractsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. High System Tracti. During high-stands, the shelf was flooded and carbonates were deposited on theouter 10-20 km. (6-12mi.) of shelf as well as the shelf margin and slope. ii. – Time of maximum siliclastic deposition in the basin was during lowstands but sands could be trapped on the shelf during a subsequent transgression e.g. In the Tansill and Yates Formations.b. Low Sand Clasticsi. – During sea-level fall, the shelf was apparently sub-aerially exposed, allowing sands and silts to be transported across the exposed shelf and deposited in the deep slope and basin ii. – The Brushy Canyon, Cherry Canyon and Bell Canyon Formations are all low-stand clastics with sequence boundaries separating one from the otheriii. Distribution of low-stand clastic deposits in the Delaware Basin. iv. Preponderance of terrigenous influx from the north and east of the Delaware basin. v. Deposition in the form of turbiditic flows with feeder channels as well as catastrophic failure of the slope margin. vi. The largest of the elongate tongues of debris have volumes compatible to large modern landslides.VIII. Oil/Gas Fieldsa. Hydrocarbons migrating out of the Delaware basin apparently moved through the Capitan reef/slope and into permeable shelf deposits up-dip from the reef. b. Hydrocarbon production from the shelf portions of the Capitan depositional system generally occur in stratigraphic and combination stratigraphic-structural trapsIX. Tengiz Fielda. Tengiz field was discovered in 1979 and is an unusually challenging field. b. The oil coming out is scalding hot and at very high pressure and the gas is high in H2S and is extremely poisonous. c. Dimension-wise the carbonate platform is 223 square miles. d. In June 1985, Tengiz T37 on the western flank blew out and was one of the world’s biggest gushers. e. Drilling at 4209 m. the well hit a high pressure zone and sent up a 200m gush of oil and hydrogen sulphide gas which ignited 2 days later. f. The fire was visible 140 km away. g. It took over a year to clear the wreckage and stop the well with a shaped charge.h. Building of the carbonate platform may have began in Upper Devonian to Lower Carboniferous times i. A hierarchy of cycles and sequences through the Carboniferous added considerable stratigraphic complexity j. A reef environment was localized to a very narrow belt within the platform margins, and sourced significant amounts of debris to the platform flanks k. Grainstones and packstones are widespread across the platform tops and are theprincipal reservoir faciesl. Karsting is also an important porosity