مدل‌سازی سازند آسماری به‌منظور تعیین میزان تولید کربنات و تامین رسوب و پارامترهای موثر بر آن در میادین نفتی انتخابی دشت آبادان

سازند آسماری توالی ضخیم کربناته تخریبی در حوضه‌ فورلند زاگرس است که در زمان الیگوسن میوسن پیشین نهشته شده است. در این مطالعه به‌منظور تعیین میزان تامین رسوب و پارامترهای موثر بر انتقال آن و میزان تولید کربنات حوضه‌ رسوبی سازند آسماری در دشت آبادان از مدل‌سازی چینه‌ای رو به جلو استفاده شده است. نرم‌افزار مطالعه‌شده، نرم‌افزار dionisos flow و میادین انتخابی شامل میادین جفیر، آزادگان، یادآوران، امید و دارخوین بوده است. سازند آسماری با ترکیب سنگ‌شناسی سنگ آهک رسی، دولومیت ماسه‌ای، سنگ آهک ماسه‌ای، ماسه‌سنگ شیلی، سنگ آهک، ماسه‌سنگ و شیل در چاههای مطالعه‌شده از 4 تا 5 توالی رسوبی تشکیل شده است. محیط رسوبی سازند آسماری در چاههای مطالعه‌‌شده شامل رمپ داخلی و رمپ خارجی (رسوبات همی پلاژیک و پلاژیک) است. پارامترهای ورودی به نرم‌افزار به‌منظور مدل‌سازی شامل داده‌های لاگ گاما، تغییرات جهانی سطح آب دریا، نقشه‌های ضخامت، نقشه‌های عمق‌سنجی دیرینه و رخساره‌های رسوبی است. بررسی داده‌های محاسبه‌شده نشان می‌دهد انرژی حاصل از امواج آب و جریان آب از عوامل موثر در انتقال رسوبات و تغییر در روند رسوب‌گذاری منطقه است. بیشترین میزان تولید کربنات در سیستم تراکت تراز پیش‌رونده‌ توالی دوم چاهها در محیط رمپ داخلی تخمین زده شده است.

Stratigraphic forward modeling of the Asmari Formation to determine carbonate production, sediment supply, and transport parameters in selected oilfields of Abadan Plain

AbstractThe Asmari Formation is a thick carbonateterrigenous succession in the Zagros Foreland Basin  deposited during the Oligocene–Early Miocene ages. The Stratigraphic forward modeling is n used in this study to determine the sediment supply, transportation parameters, and production rate of the Asmari Formation during precipitation in the Abadan Plain. The Dionisos Flow software is used for modeling studied depositional sequences. Argillaceous limestones, sandy dolostones, sandy limestones, sandy shales, limestones, sandstones, and shales are the main lithology of the Asmari Formation in studied wells. Also, the studied formation consists of four to five depositional sequences in the studied wells. The sedimentary environment of the Asmari Formation in the selected wells includes the inner to outer ramp (hemipelagic and pelagic deposits). The input parameters to the software for modeling include gamma log data, global sealevel curve, thickness and bathymetry maps, as well as sedimentary facies. Examination of the calculated data shows that the wave energy and water flow rate are effective factors in the sediment transportation and change in the sedimentation process of the region. The highest rate of carbonate production is estimated in the transgressive system tract of the second depositional sequence of studied wells in the inner ramp environment.Keywords: Sediment Supply, Carbonate Production, Asmari Formation, Abadan Plain, Dionisos Flow Software.  IntroductionStratigraphic forward modeling is one of the branches of sedimentary basin modeling that helps petroleum geologists to better understand the variation of depositional sequences in carbonate and terrigenous environments. The Dionisos Flow software can calculate and visualize sediment supply, subsidence, and carbonate production rates over geological time. Thus, this software helps to model the stratigraphic variation in a selected basin.The Asmari Formation (Oligocene–Early Miocene ages) is known as one of the most important carbonate formations in Iran due to its high reservoir capacity. In this study, the Asmari Formation was investigated by the Dionisos Flow to demonstrate stratigraphic forward modeling during precipitation in the Abadan Plain.Material Methods Dionisos Flow Software was used to determine the sediment supply and carbonate production rates of the Asmari Formation in five oil fields (six wells) of the Abadan Plain. Selected oilfields include Jufeyr, Azadegan, Yadavaran (Kusk and Hosseiniyeh), Omid, and Darquain.  Input parameters to the software include gamma log data, global sealevel curve, depth and thickness maps, bathymetry data, and sedimentary facies. Firstly, these data are changed to numeric data. Then, these data are processed by Dionisos Flow Software for calculating parameters that are used for modeling.The geometry of the sedimentary basin of the Asmari Formation in the study area includes X=160 (length) and Y=100 km (width). The forward stratigraphic modelling is performed from the past to the present in a sequence of time steps. Therefore, in this study, the age from the beginning to the end of the simulation has been determined 33.19–9.4My with using palaeontological data in palaeolog information of each of the studied wells and strontium isotope dating studies. Discussion of Results ConclusionThe main lithology of the Asmari Formation in the  studied wells are argillaceous limestones, sandy dolostones, sandy limestones, sandy shales, limestones, sandstones, and shales. This formation in the studied wells consists of four to five depositional sequences. The first depositional sequence of each well includes deep to semideep facies (mainly clayey limestones) and belongs to the lower part of the Asmari Formation with the Rupelian age. The second to fifth depositional sequences of the Asmari Formation in the studied wells mainly consist of sandstones and shaly sandstones, and according to the constituent facies, belong to the inner ramp environment. These depositional sequences were found in the upper part of the Asmari Formation with the Aquitanian age.A study of stratigraphic forward modeling in depositional sequences of the Asmari Formation shows that the sediment supply rate per unit time for each of the depositional sequences was controlled by two main parameters, including global sealevel changes and tectonic processes in the region.Also, the factors that were affecting sediment transport were the water flow rate and wave energy. The energy from the water waves in the fifth depositional sequence is estimated at 48.2 KW/m, which decreases with the increase of depth in the lower depositional sequences of the formation. The highest rate of carbonate production is estimated in the transgressive system tract of the second depositional sequence in the inner ramp environment.