Regional Stratigraphy, Sedimentology and Petroleum Geology of the Grand Rapids Formation, Mannville Group, Northeastern Alberta

摘要: ABSTRACT In northeastern Alberta, the Grand Rapids Formation comprises upper part of regressive Upper Mannville Group and consists dominantly thick sandstones. Regional correlations to south show that sands were fed from a number incised valleys cutting Waseca, McLaren Colony formations Lloydminster area. The sandstones are therefore falling lowstand sea level deposits which offlap surfaces equivalent updip unconformities. Six allostratigraphic units defined on basis erosion cut at bases shorefaces transgressive their tops have been defined. Each offlapping unit in thin channel crevasse-splay grading northward into major shoreface sands. largest very extensive, reaching dimensions 100 km by 200 50 m thickness because they composite, consisting several individual as well valley fills. Individual within these larger composite bodies extend seaward few kilometres tens before clinoforming terminating downlap. They southward with abrupt facies terminations finer-grained deposits. Alongshore, onlap against other discharged different or, west, successions. Relative fluctuations caused incision amalgamation As result lack seals, reserves hydrocarbons (both bitumen gas) generally not accumulated thickest but thinner uppermost sandstone is effectively blanketed overlying Joli Fou Shale. Hydrocarbons may be trapped lower situations where intervening shales preserved form an effective seal. north gas fields. Many occur small drape structures postsedimentary dissolution Devonian salt. Smaller pools stratigraphic traps permeable terminate changes. RESUME Dans le nord-est de l'Alberta, la englobe partie superieure du groupe superieur en regressivite et consiste surtout gres epais. Les regionales vers sud indiquent que les sables ont ete alimentes par des vallees encaissees tranchant region Lloydminster. consequent s'effondraient depots au plus bas niveau mer equivalentes discordances amont-pendage. unites allostratigraphiques definies selon d'erosion tranchees base zones infratidales transgressives leur sommet definies. Chaque unite allostratigraphique fluviatile mince crue causee une fissure qui se nivelle nord jusqu'a zone importante infratidale gres. importants dimension peuvent atteindre d'epaisseur parce qu'ils sont composes plusieurs individuels ainsi taillees remplies. parmi masses composees importantes s'etendent quelques dizaines avant prendre forme talus subaquatique terminer couches inclinees sur discordance. Ils terminent biseau avec abruptement grains fins. Le long rivage, chevauchent contre d'autres provenant ou, l'ouest, successions fins superieur. 1 Geological Survey Canada Contribution No. 1996508 End_Page 141------------------------ variations relatives cause l'encaissement l'alliage infratidales. A manque d'obturations, grandes d'hydrocarbures (bitume gaz naturel) ne pas generalement accumulees dans epais, mais minces superieures recouvertes schiste Fou. hydrocarbures etre pieges inferieurs lorsque schistes traversent conserves facon former obturation solide. bitume est piege champs petroliferes importants. Plusieurs situent petites draperies presentent pre-sedimentaire sel devonien. petits gisements produisent stratigraphiques ou permeables amont-pendage changements facies. Traduit Marie-Louise Tomas