Identification and Prediction for the Subtle Oil Reservoir Developed at Yongjin Area in Junggar Basin

摘要

The Yongjin Oil field had been explored to be a large oilfield with in-placevolume of hundreds millions ton in Junggar Basin.It had been proved by drilling datathat its oil reservoirs were mainly the basal conglomerate reservoir entrapping inCretaceous,sandstone reservoir below the coal bed and stratigraphic-lithologicreservoirs above the coal bed entrapping in Jurassic Xishanyao Group.It was difficultto predict and evaluate the reservoirs due to deep buried target,thin sandstonedeveloped and poor reservoir physical property,which made the hydrocarbonexploration difficult at present.The factors controlling lithologic or stratigraphic-lithologic reservoirs and itscorresponding matching relationships had been studied through using high accuracysequence stratigraphy,reservoir seismic prediction techniques and strata unconformityanalysis basing on regional geologic background and subtle oil reservoir charactersanalysis.Finally the subtle traps had been analyzed and evaluated through analyzingreservoir physical property,porocity and prestack property oilness prediction,comprehensive unconformity and stratigraphic-lithologic traps analysis,and then thebenefit reservoir development zone and two benefittargets had been predicted for drilling.The sequence stratigraphic time and space framework for Jurassic and Cretaceousbottom had been built according to individual well sequence analysis and seismic datalateral tracing combining with geologic data,geophysical exploration data andlogging data,as a result eight third order sequence interfaces depositing at Jurassicand Cretaceous bottom had been classified.Four types deposit facies(braided stream,meandering stream,delta and lakes) had been determined through studyingdepositional system and depositional facies finely.The conditions for subtle trapsconfiguration and their controlling factors had been studied to build correspondingsequence stratigraphic model for hydrocarbon entrapment.The seismic identification and description methods applied to analyzing subtletraps had been studied systematically in order to determine structure geometry andfractures distribution and predict reservoirs distribution in space,which wereconsisted by trap identification technique,reservoir prediction and hydrocarbon prediction techniques.The individual sandstone distribution in plain had beenidentified through seismic inversion with Gr curve for the benefit depositional facieszone.The reservoir physical property had been analyzed and classified throughproperties analysis and spectrum decomposition method.The variable velocitymapping was used to resolve questions of velocity great change in lateral and timeand depth transformation under conditions of deep buried dept.it could be used toidentify low amplitude structure.The coherence analysis,dip and azimuth scanningand frequency division amplitude were all applied to identify strata pinchoutboundary and describing correctly faults distribution.The inversion technique usedcould differ sandstone and mudstone each other when they could not separated fromeach other using conventional method.The property analysis basing on constraininversion was applied to predict reservoirs physical property and their development.The hydrocarbon could help predicting subtle traps bearing hydrocarbon.The subtle traps had been evaluated comprehensively to optimize the targets fordrilling and provide reliable evidence after the reservoirs developed at Cretaceous-Jurassic had been predicted and described through analyzing unconformities structureand their physical property,porosity and pre-stacked extracted property,identifyingstrata onlapping and denudation zoneAs a result of study three new techniques had been developed.They are asfollowing①The developed technique for identifying correctly thin sandstones developed indeep formation in Yongl well areaThe variable velocity mapping was used to resolve questions of velocity greatchange in lateral and time and depth transformation under conditions of deep burieddept.it could be used to identify low amplitude structure.The coherence analysis,dipand azimuth scanning and amplitude spectrum obtained by frequency division wereall applied to identify strata pinchout boundary and describing correctly faultsdistribution.②The developed inversion technique with less wells drilled for thin sandstonecharacters prediction in Yongl well area.It was difficult to use only the impedance to predict correctly reservoir distributiondue to impedance overlapping in the area of benefit reservoir and non reservoir.So itwas first developed that combining logging data to reconstruct characters property reflecting the change of reservoir in space at well drilled,and then applying neuralnetwork technique to inversing the characters cube,by with finally the reservoirdistribution in space could be predicted correctly.③The developed technique for evaluating reservoirs in Yongl well areaThe reservoir developed characters had been predicted combining variableprediction and evaluation techniques from different respects.Firstly it used inversiontechnique constrained with pseudo acoustic impedance and Gr curves to predictsandstones.Secondly the reservoirs physical property had been calculated in quantity.Finally a AC model had been built to predict porosity,the oil saturation had beenpredicted with sequential gaussian simulation modeling,the reservoir oilness hadbeen predicted using spectrum decomposition and prestack AVO analysis,as a resultan effective prediction and evaluation for reservoir had been developed.

目录

Abstract

1 Introduction

1.1 Project Foundation and Significance

1.2 Present Situation of Research Home and Abroad

1.2.1 Present situation of research and development tendency abroad

1.2.2 Classification and feature for subtle reservoirs

1.2.3 Progress in stratigraphic hydrocarbon reservoir exploration technologies home and abroad

1.3 Research Content and Technique Course

1.3.1 Research content

1.3.2 Technique process

1.4 Major Research Results and Innovation

1.4.1 Major research results

1.4.2 Innovation

2 Geologic background and subtle pool feature in Yongjin Oilfield

2.1 Formation Feature

2.1.1 Formation development feature

2.1.2 Stratigraphic distribution feature

2.2 Main Structural Feature and Basin Evolution

2.2.1 Structural features

2.2.2 Palaeohigh formation and evolution

2.2.3 Impact of the palaeohigh evolution on the tectonic deformation of each block

2.3 Reservoir Bed Features and Reservoir-capping Combination

2.3.1 J_2x group of jurassic system

2.3.2 Cretaceous system

2.3.3 Physical poroperty features

2.3.4 Reservoir-capping combination

2.4 Subtle Pool Features and Forming-reservoir Patterns

2.4.1 Subtle pool features

2.4.2 Formed subtle reservoir form patterns

2.4.3 The control factors for the formed reservoir

3 Sequenc Stratigraphy Aanlysis

3.1 Sequence Stratigraphic Feature

3.1.1 Sequence interface identification

3.1.2 Sequence stratigraphic classification and comparison

3.2 Distribution of Depositional System

3.2.1 The sedimentary facies analysis and sedimentary system distribution for J_2x group

3.2.2 The bottom block sandstone facies and its deposit system at K_1q group

4 Reservoir Seismic Prediction Techniques

4.1 Geologic Background and Seismic Data Analyzing

4.1.1 The pool basic feature

4.1.2 The analysis for seismic data quality in the area

4.2 Seismic Prediction for Reservoirs

4.2.1 The seismic properties for reservoir prediction

4.2.2 Reservoir physical property prediction

5 The Subtle Trap Identification and Evaluation

5.1 Unconformity Structure and Its Distribution

5.1.1 The structure for the unconformity

5.1.2 The unconformity lithologic and logging response

5.1.3 The unconformity seismic response

5.1.4 The influence on reservoir property caused by unconformity development

5.1.5 The unconformity texture prediction

5.2 Subtle Traps Identification and Assessment

5.2.1 The difficulty and solution

5.2.2 Subtle traps fine description

5.2.3 Hydrocarbon abundance entrapped prediction

5.2.4 Traps evaluation

6 Conclusion and Suggestion

6.1 Conclusion

6.2 Suggestion

Reference

Acknowledgment

Resume

Issued Artieles