Pliocene hyperpycnal flow and its sedimentary pattern in D block of Rakhine Basin in Bay of Bengal

Based on core,logging,lab test and seismic data,sedimentary characteristics and pattern of marine hyperpycnal flow,the distribution rules of hyperpycnal flow reservoir,prediction method of favorable hyperpycnal flow reservoir zones,hydrocarbon accumulation model in hyperpycnal flow reservoir in D block of Bay of Bengal were investigated,and the favorable exploration zone and well sites were predicted.Pliocene in D block has typical hyperpycnal flow sediment,which is a set of fine-medium sandstone held between thick layers of marine mudstone and features a series of reverse grading unit and normal grading unit pairs.The hyperpycnal flow sediment appears as heavily jagged box shape,bell shape and tongue shape facies on log curves with linear gradient,and corresponds to multiple phases of deep channels on the seismic section and high sinuous channel on stratal slices.The sedimentary bodies formed by a single phase hyperpycnal flow which include five types of microfacies,namely,supply channel(valley),channel complex,branch channel,levee and sheet sand.The hyperpycnal flow sediments appear in multiple branches,multiple generations and stages in space,forming high-quality reservoirs in strips on the plane and superposition vertically,with fairly good physical properties.The channel complex sandstone,with large thickness,coarse particle size and good physical properties,is the most favorable exploration facies.Based on the guidance of the sedimentary model,distribution of the channel complex microfacies was delineated in detail by seismic reflection structure analysis,spectrum waveform characteristic analysis,slice and attribute fusion,and combined with the structural feature analysis,the favorable drilling zone was sorted out,effectively guiding the exploration deployment of the block.

An intelligent automatic correlation method of oilbearing strata based on pattern constraints:An example of accretionary stratigraphy of Shishen 100 block in Shinan Oilfield of Bohai Bay Basin,East China

Aiming at the problem that the data-driven automatic correlation methods which are difficult to adapt to the automatic correlation of oil-bearing strata with large changes in lateral sedimentary facies and strata thickness,an intelligent automatic correlation method of oil-bearing strata based on pattern constraints is formed.We propose to introduce knowledge-driven in automatic correlation of oil-bearing strata,constraining the correlation process by stratigraphic sedimentary patterns and improving the similarity measuring machine and conditional constraint dynamic time warping algorithm to automate the correlation of marker layers and the interfaces of each stratum.The application in Shishen 100 block in the Shinan Oilfield of the Bohai Bay Basin shows that the coincidence rate of the marker layers identified by this method is over 95.00%,and the average coincidence rate of identified oil-bearing strata reaches 90.02% compared to artificial correlation results,which is about 17 percentage points higher than that of the existing automatic correlation methods.The accuracy of the automatic correlation of oil-bearing strata has been effectively improved.

Sedimentary characteristics and processes of the Paleogene Dainan Formation in the Gaoyou Depression, North Jiangsu Basin, eastern China

In this paper,the type,vertical evolution,and distribution pattern of sedimentary facies of the Paleogene Dainan Formation in the Gaoyou Depression of the North Jiangsu Basin are studied in detail.Results show that fan delta,delta,nearshore subaqueous fan,and lacustrine facies developed during the Dainan Formation period and their distribution pattern was mainly controlled by tectonics and paleogeography.The fan delta and nearshore subaqueous fan facies predominantly occur in the southern steep slope region where fault-induced subsidence is thought to have created substantial accommodation,whereas the delta facies are distributed on the northern gentle slope which is thought to have experienced less subsidence.Finally,the lacustrine facies is shown to have developed in the center of the depression,as well as on the flanks of the fan delta,delta,and nearshore subaqueous fan facies.Vertically,the Dainan Formation represents an integrated transgressiveregressive cycle,with the E2d1being the transgressive sequence and the E2d2being the regressive sequence.This distribution model of sedimentary facies plays an important role in predicting favorable reservoir belts for the Dainan Formation in the Gaoyou Depression and similar areas.In the Gaoyou Depression,sandstones of the subaqueous distributary channels in the fan delta and the subaqueous branch channels in the delta are characterized by physical properties favorable for reservoir formation.

Controls on the facies and architecture evolution of a fan delta in Qinghai Lake,China

Deltaic sedimentary systems form the most favorable hydrocarbon reservoirs in continental faulted lacustrine basins,and their types and controlling factors directly affect the distribution of hydrocarbons.The systematic study of typical modern delta deposition provides significant guidance regarding the distribution of oil and gas reservoirs in the subsurface.For this reason,the Heima River delta in Qinghai Lake,which features multiple sediment sources and clear sedimentary evolution stages,was selected for this research.A detailed study of the sedimentology and architectural characteristics of the Heimahe delta in Qinghai Lake was conducted.A total of 4 types of gravel facies,4 types of sand facies,and 2 types of mud facies were identified.This study also focuses on recognizing the architectural elements within channels and bars.The delta plain features debris-flow,switched,and migrated channels and vertical and bilateral aggradation bars.The delta front features migrated and filled channels and bilateral and lateral aggradation bars.Twenty-two representative outcrop sections were selected.Detailed observation and analysis of these sections revealed three stages:the progradation to aggradation(PA)stage,in which the deposits show evidence of sigmoid-type and coarse-grained sedimentation;the retrogradation(R)stage,which is characterized by imbricated regression;and the aggradation to progradation and degradation(APD)stage,which is characterized by a terraced-stepping,progression stacking pattern.Based on the integrated analysis of the sedimentary environment,outcrop lithofacies associations,architecture stacking patterns,fossils and bioclasts,we identified diverse depositional associations and constructed a sedimentary evolution model of the depositional system in this area.We suggest that the depositional system transitioned from an early single-provenance gravel-rich fan delta to a multi-provenance mud-rich delta and that two factors mainly controlled the transition:the southern boundary fault activity and lake level variations.The contemporaneous activity of the fault increased the accommodation in the low-stand systems tract,which resulted in continuous coarse-sediment deposition.