Mauddud Formation Research Articles

Comparison of the Petrophysical and Reservoir Heterogeneity of the Mauddud Formation in Halfaya and Ratawi Oil Fields, Southern Iraq

Comparison of the Petrophysical and Reservoir Heterogeneity of the Mauddud Formation in Halfaya and Ratawi Oil Fields, Southern Iraq

Microfacies Analysis and Evolution of Porosity of the Albian-Early Cenomanian Mauddud Formation from Selected Wells in Ratawi Oilfield, Southern Iraq

Mauddud Formation (Albian stage-the Early Cretaceous) is an important oil reservoir in Ratawi field of southern Iraq. Four wells, R T-2, R T-3, R T-6, and R T-7, located 70 km northwest of Basra, were selected to study microfacies properties and petrophysical associations with the probability of oil production. Seventy-seven core samples are collected, and thin sections for petrographic analysis. The self-potential, Gamma-ray, resistivity, and porosity logs are used to determine the top and bottom of the Mauddud Formation. Water saturation of the invaded and uninvaded zones, shale volume, and porosity were calculated. The study area results showed that the quantity of shale is less than 15% for most of the wells, and the dominant porosity is the secondary porosity. In contrast, the primary porosity is low in all study wells, and the formation contains varying proportions of producing hydrocarbons. The results suggest the formation comprises light-colored dolomitized lime and pseudo-oolitic white limestone with green to blue-gray shale. The petrographic analyses of 65 thin sections of the Mauddud Formation reveal that most skeletal grains are shallow marine-derived faunas, while non-skeletal grains include peloids and ooids. The facies analysis showed that the Mauddud Formation was deposited within different sedimentary environments ranging from deep to very shallow environments, which was represented by a large variation in Five microfacies and ten submicrofacies, the microfacies "Mudstone, wackestone, packstone, grainstone, and Rudstone "submicrofacies" Peloidal wackestone to packstone, Bioclastic wackestone to packstone, Miliolids wackestone to packstone,Orbitolina wackestone, Peloidal packstone to grainstone, Orbitolina packstone, Mudstone to wackestone,Bioclastic wackestone, Miliolids and Bioclastic wackestone to packstone, Bioclastic packstone, and Peloidai grainstone". This variance suggested that the formation might be deposited within the carbonate platform's variety of environment, such as "deep sea, restricted, shallow open marine, mid-ramp, rudist biostrome, and shoal." Seven different kinds of pores have been found in the carbonate sideman of the Formation: Interparticle, Intraparticle, moldic, Vuggy and fracture.

Petrophysical Characteristics of Mauddud Formation in Selected Wells of Ratawi Oilfield, Southern Iraq

The Mauddud Formation is the most widespread Lower Cretaceous formation in Iraq, deposited along the NE margin of the Arabain Palte. The formation is widely distributed, covering nearly the entire territory of Stable and Unstable Shelf units. The study area is located in the Zubair subzone of the Mesopotamian zone within the Stable Shelf unit, approximately 70 km northwest of Basrah in southern Iraq. The main goal of this study is to evaluate the petrophysical characteristics of Mauddud Formation in the five wells (Ratawi-2, Ratawi-4, Ratawi-5, Ratawi-17, and Ratawi-19) in the Ratawi oilfield, southern Iraq. Open hole log analysis was utilized, and a series of calculations were applied to evaluate the reservoir properties, such as porosity, water saturation, and volume shale, that control the reservoir quality. The N-D cross plot diagram shows that limestone is the dominant lithology, and few shale contents is present in the upper and lower parts of the formation, while it is noticed that the volume of clay is constant throughout the formation in most of the wells, indicating that the formation is clean. Seven zones (A to G) have been identified and evaluated, depending mainly on full set logs to determine the most productive ones. Zones B, D, and F are classified as good reservoir zones with an average porosity of 21% and water saturation of 25%. A and C zones show reservoir and non-reservoir zones with porosity of 10% and water saturation of 40%. Finally, the remaining zones represented by E and G are classified as non-reservoir zones with a very low porosity of less than 4% and fully water-saturated.

Evaluation of Petrophysical Properties of Mishrif, Rumiala, Ahmadi, and Mauddud Formations in Nasiriya Oil Field—Middle of Iraq

Evaluation of Petrophysical Properties of Mishrif, Rumiala, Ahmadi, and Mauddud Formations in Nasiriya Oil Field—Middle of Iraq

Large Benthic Foraminifera Biozonation of Mauddud Formation in Selected Section from Balad Oil Field, Central Iraq

Three subsurface sections Ba-1, Ba-4, and Ba-8, and sixty-five thin sections were examined to investigate the biostratigraphy of the Mauddud Formation (age Early Albian - Late Cenomanian) within the Balad Oil Field located in central Iraq. The formation is lithologically composed of dolomitic limestone, creamy oolitic limestone, and shale. Orbitolina qatarica, Orbitolina sefini, and Orbitolina concava range zones were distinguished as biozones, including the Late Albian (Orbitolina qatarica), Late Albian to Early Cenomanian (Orbitolina sefini), and Early-Cenomanian (Orbitolina concava) zones. The age of these biozones confirmed the extent throughout the early Cenomanian age. Fossils of twenty-seven species of Foraminifera, including Conicorbitolina conica, Miliolids, Neoiraqia convexa, Nezzazata, orbitolina sp., Spiroluculina sp., and Trocholina sp., and others like Coral, gastropods, and rudest were identified.

Microfacies Analysis and Diagenesis Processes of Mauddud Formation in selected wells from Ratawi oil field, Southern Iraq

Mauddud Formation was studied in Ratawi oil field, Southern Iraq. The lithology of the formation is limestone in all studied wells (Rt-2, Rt-4, Rt-17 and Rt-19). lower contact of Mauddud Formation with Nahr Umr Formation is gradational, but the upper contact is unconformable with Ahmadi Formation. In this work, 114 thin sections were examined and shows four microfacies (wackestone, packstone, grainstone and argillaceous mudstone), which deposited in the Inner-Mid to Outer ramp environment. The most significant diagenesis processes were micritization, dissolution, cementation, compaction, and dolomitization, which had an impact on the texture and porosity of the Mauddud Formation.

Advanced Geostatistical Techniques for Building 3D Geological Modeling: A Case Study from Cretaceous Reservoir in Bai Hassan Oil Field

A 3D Geological model was generated using an advanced geostatistical method for the Cretaceous reservoir in the Bai Hassan oil field. In this study, a 3D geological model was built based on data from four wells for the petrophysical property distribution of permeability, porosity, water saturation, and NTG by using Petrel 2021 software. The geological model was divided into a structural model and a property model. The geological structures of the cretaceous reservoir in the Bai Hassan oil field represent elongated anticline folds with two faults, which had been clarified in the 3D Structural model. Thirteen formations represent the Cretaceous reservoir which includes (Shiranish, Mashurah, U.kometan, Kometan Shale, L. Kometan, Gulneni, Dokan, Mauddud, Jawan/Mud, Batiwah, Shuaiba, Garagu, L.Sarmord). According to the property model, the model for each petrophysical property was constructed based on core data and CPI. By using the geostatistical method, the property model was constructed. The Mauddud Formation is considered one of the most promising hydrocarbon reservoirs in the Bai Hassan oil field based on the results of the property model, where the ratio of water saturation is around 30%, the porosity value is reaching up to 31%, and the net to gross ratio is averaging at 70%.

Integrated the Core Analysis Data, Image logs, and Conventional Logs to Understand the Reservoir Rock Type of the Mauddud Formation

Integrated the Core Analysis Data, Image logs, and Conventional Logs to Understand the Reservoir Rock Type of the Mauddud Formation

Biostratigraphy and Microfacies of the Mauddud Formation (Late Albian – Early Cenomanian) in Musaiyib Well No.1, Central Iraq

Upper Albian and Lower Cenomanian biostratigraphy and microfacies types of the Mauddud Formation from Musaiyib well No.1, Central Iraq are described and examined, which consists of thick to medium bedded limestone, marly limestone rich in argillaceous material, green shale, and dolomitic limestone beds. Thirty-six species from twenty-two genera of benthic foraminifera in addition to calcareous algae, coral, bivalves, gastropods, rudist fragments, brachiopods, bryozoan, and echinoid fragments are recognized from the Mauddud Formation of the studied well. On the basis of the recognized benthic foraminifera three biozones were determined: Mesorbitolina texana - Orbitolina qatarica Concurrent Range zone- Orbitolina sefini-Total R. Zone and Orbtolina concava Total R. Zone. Both suggest the Late Albian – Early Cenomanian age. The results of this study are compared with the work of others inside and outside Iraq. Based on the petrographical analyses, four major microfacies (Mudstone, wackestone, wackestone to packstone, and packstone), and nine sub-microfacies were identified. The Mauddud Formation was formed in a marine environment that was composed of the following three sub-environments: the inner ramp and the middle to the outer ramp.

Carbonate Ramp Facies and Porosity Recognition: Case Study of the Late Albian-Early Cenomanian Mauddud Formation in Ratawi Oilfield, Southern Iraq

The carbonate ramp facies of the Late Albian-Early Cenomanian Mauddud Formation were studied in the Ratawi Oilfield, Basra Governorate, south of Iraq using integrated borehole data set that included, core and cutting samples in three drilled wells to analyze the petrography of the Mauddud Formation, two hundred and eighty-one (281) thin sections were prepared and examined for the three selected wells. The results show that the formation is composed of light grey dolomitized limestone and pseudo-oolitic creamy limestone with green to bluish shale. The petrographic observations results show four facies’ associations in the Mauddud Formation. These include: Mid–Ramp environment which is represented by Argillaceous mudstone microfacies, Argillaceous wackestone microfacies and orbitolinid wackestone microfacies; the shallow open marine environment which is assimilated by foraminiferal wackestone microfacies and foraminiferal packstone microfacies; a restricted marine environment that represented by bioclastic fossiliferous wackestone microfacies and miliolid wackestone microfacies and Shoal environment is represented by bioclastic packstone microfacies, bioclastic grainstone microfacies, peloidal foraminiferal pack-grainstone microfacies, and peloidal packstone-grainstone microfacies with diverse skeletal grains. The porosity includes Vuggy, Interparticle, Intraparticle and Fracture porosity.

Biostratigraphy of the Mauddud Formation from selected Boreholes, central Iraq

The Mauddud Formation was one of the important and widespread Lower Cretaceous period formations in Iraq. It has been studied in three wells (EB. 55, EB. 58, and EB. 59) within the East Baghdad Oil Field, Baghdad, central Iraq. 280 thin sections were studied by microscope to determine fauna, the formation composed of limestone and dolomitized limestone in some parts which tends to be marl in some parts, forty species and genus of benthic foraminifera have been identified beside algae and other fossils, three biozones have been identified in the range which is: Orbitolina qatarica range zone (Late Albian), Orbitolina sefini range zone (Late Albian – Early Cenomanian) and Orbitolina concava range zone (Early Cenomanian), The age of the Mauddud Formation was determined using these three biozones, and it was then suggested that the formation was Late Albian–Early Cenomanian based on careful comparison and correlation with foraminifera species found locally and globally.

High-Resolution Sequence Stratigraphy of the Mauddud Formation Southern Iraq

Inner ramp carbonate and dolomitic limestone made up the late Albian Mauddud reservoir in Iraq. An age estimate for the Mauddud Formation is late Albian to early Cenomanian, with it overlying the Nahr-Umr Formation and underlying the Ahmadi Formation. The integration of microfacies with wireline logging data to predict the high resolution of the sequence stratigraphy framework. The microfacies description included more than 150 thin sections that covered the study area in southern Iraq. That results in five main microfacies. There are divided into eleven submicrofacies, as a result, for the microfacies, the depositional environment is gradual, from mid-ramp to shallow open marine, shoal-restricted lagoon. The study divided the formation into four orders of sequence stratigraphy: MSL1, MSL2, MSL3, and MSL4. The study includes identifying the maximum flooding surface (K110), which is identified as the original transgression in sea level that covered Arabian Plate. MSL1 represents the lower part of formation and evidence of environmental change to shall the marine environment with argillaceous limestone. The maximum flooding surface (K110) is signifying the deepest depositional environment (mid-ramp). Also, the study marked three marine flooding surfaces by changes as increased gamma ray and density logs values, whilst the highstand system reflects decreasing in logs values, This change was used in conjunction with microfacies data to construct the sedimentological environments that led to the documentation of the Mauddud high-resolution sequence stratigraphy framework.

Depositional Architecture and Stratigraphic Framework of Albian Succession in Balad and Nasiyia Oil Fields

The Albian Carbonate-clastic succession in the present study is represented by the Mauddud and Nahr Umr formations were deposited during the Albian stage within the Wasia Group More than 200 thin sections of cores and cuttings in addition to well logs data for Nahr Umr and Mauddud formations from 4 boreholes within two oil fields (Ba-4, Ba-8, Ns-2 and Ns-4) were used to interpret the different associations facies as well as the facies architectures to describe the sedimentary framework of the basin and development the petrophysical properties. Seven major microfacies were diagnosed in the carbonate succession of the Mauddud Formation, while the Nar Umr Formation includes five lithofacies; their grain types characteristic and depositional textures enabled to recognize of paleoenvironments. These microfacies were deposited in restricted, shallow open marine, back-reef, slope and deep open marine for the Mauddud succession. While in Nahr Umr, the lithofacies were deposited in bay fill, back-shore and distributary channel. The studied succession in Balad oil field which represents two 3rd order and four 4th order cycles (A1, A2, A3 and A4). These cycles are asymmetrical and starts with cycle A1 where the Backshore facies in Lower Mauddud Formation represents the transgressive systems tract and then appear the hightstand systems tract bounded below by a transgressive surface which coinside with the unconformable surface with the underlying Shuaiba Formation. In Nasyria oil field the studied succession represents two 3rd order cycles and three 3rd order cycles (A1, A2 and A4) with absence of A3 cycle. These cycles are asymmetrical and starts with cycle A1 where the distributary channel in the lower part of Nahr Umr succession represents the transgressive systems tract bounded below by unconformable surface with the underlying Shuaiba Formation. The highstand systems tract of cycle A1 is reflected by shallowing upward for distributary channel, bay fill and back-sore facies of the Nahr Umr Formation. This relatively thick parasequence reflect time of sea level stillstand where tectonic subsidence is the major controlling factor on producing the necessary accommodation for thick aggregational to progradation clastic succession to deposit.

Petrophysical Properties of Mauddud Formation in Selected Wells in Al-Ahdab Oil Field, Middle Iraq

This paper aims to calculate the petrophysical properties in the Al-Ahdab field in the middle of Iraq within the Mauddud Formation. This study was based on the information available from well logs. The interactive petrophysical software IP (V4.5) was used to calculate the porosity, hydrocarbon saturation and shale volume, divide the formation into reservoir units and buffer units, and evaluate these units in each well. The Mauddud was divided into five units, two of them were considered good reservoirs having good petrophysical properties (high porosity, Low water saturation, and low shale volume). The other three are not reservoirs because of poor petrophysical properties.

3D Petrophysical Modeling of Mauddud Formation at Ratawi Oil Field, Southern Iraq

3D Petrophysical model for Mauddud Formation in Ratawi oilfield had been created. Five wells have been chosen in Basra governorate to construct Structural and petrophysical (effective porosity, water saturation and Net /Gross) models. Structural model showed that Ratawi oilfield composed of one anticline fold, where its axis extends toward North to South. After creating zones for Mauddud Formation, which was divided into 5 zones i.e. A, B, C, D and E zone. Layers were built for each zone according to petrophysical properties. A, B and D units were divided in 1 layers as a barrier, While the unit B was divided into 25 layers and the unit D was divided into 15 layers because it represents reservoir zones. The 3D grid of Mauddud Formation model that was built consists of (841295) cell and each cell have dimensions I =91 * J =215 * K =43. Finally, Petrophysical models (effective porosity, water saturation and Net /Gross) had been constructed for each zone of Mauddud Formation. Based on data analyses and results from modelling, the B then D is a important reservoir unit in terms of its good properties (high effective porosity, low water saturation) and increase in production periods from the thickness of the total reservoir.

تقييم صخور الكربونات في الصحراء الغربية للعراق كأحجار أبعاد للبناء

تم تقییم الصخور الكاربوناتية كصخوربعدية للبناء. تم جمع الصخور الكاربوناتية من تكوين مودود (الباين-سينومانين) من الصحراء الغربية العراقية وقد تم دراستها بتروغرافيا، معدنيا وجيوكيميائيا. الخواص الفيزيائية والميكانيكية للنماذج المختارة تم ايجادها لتقييم ملائمتها كصخور بناء. تم تنفيذ العمل الحقلي والتقييم بنمذجة ثلاثة مواقع من الصخور الكاربوناتية. تم دراسة البتروغرافية والمعدنية لهذه الصخور باستخدام المجهر المستقطب وتقنية الاشعة السينية الحائدة وقد تم تمييز ثلاث سحنات دقيقة (دمالق الواكي-المرزوم، دمالق المرزوم والكاربوني المتبلور). الدلمتة، السمنتة واعادة التبلورهي العمليات التحويرية الرئيسة والمؤثرة على الخواص الفيزيائية والكيميائية لها. الدولومايت هو المعدن الغالب في المواقع 1M و2M بينما الكالسايت هو المعدن الغالب في موقع 3M.تم تحلیل النماذج كيميائيا لاوكسيد السليكون، اوكسيد الالمنيوم، اوكسيد الكالسيوم، اوكسيد المغنيسيوم، اوكسيد الحديديك، اوكسيد الصوديوم، اوكسيد البوتاسيوم، اوكسيد التتانيوم، اوكسيد المنغنيز ومفقودات الحرق. وكانا اوكسيدي الكالسيوم والمغنيسيوم هما الاوكسيدين الغالبين مؤكدين وفرة الكالسايت والدولومايتلذلك صنف كدولومايت كالسيتيفي المواقع 1M و2M بینما صنف على انه لايمستون فی الموقع 3M. اشارت نتائج تحليلات الخواص الفيزيائية والميكانيكية (الكثافة الكلية ، الامتصاص المائي، قوة الضغط، معايير الكسر ومقاومة الحك) ان الصخور المختارة كانت مناسبة كصخور بعدية للبناء اعتمادا على المواصفات الامريكية القياسيةلاختبار المواد.

Facies Analysis and Depositional Environments of the Nahr Umr Formation in Rumaila Oil Field, Southern Iraq

The Nahr Umr Formation (Albian) was studied in the Rumaila oil field, southern Iraq. It consists of sandstone with high porosity and permeability, and contains a few shale overlaps that permeate the sandstone in the lower part of it, while it consists of shale and a few limestone rocks from the electrification in the upper part. The upper contact surface of this formation is conformable and graded with the Mauddud Formation. The limestone at the base of the Mauddud Formation may be on top of the black shale of the Nahr Umr Formation, and this formation is bounded from below by the Shuaiba Formation in an unconformable, which corresponds when the black shale of the Nahr Umr Formation sits on the limestone to form the Shuaiba Formation. The monocrystalline Quartz mineral is the major component of the Sandstone, with small percentages of polycrystalline quartz, feldspar, and rock fragments, according to the petrographical investigation. Mineral and textural maturity were present in the formation of rocks. Compaction, cementation, were the most important processes that influenced the rock characteristics of Nahr Umr's sandstone rocks. Six lithofacies shale, lenticular bedded sandstone–mudstone, false bedded sandstone–mudstone, siltstone–shale, cross-bedded sandstone, and parallel and cross-lamination sandstone were identified as representing the different sub environments within the different parts of transitional environments (fluvial and deltaic depositional environments), which represented oscillations in sea level rise and stillstands of the relative sea level controlled by tectonics as sediments of the basin transitioned from freshwater to marine conditions.

Biostratigraphy of the Early Cretaceous Mauddud Formation in Ratawi Oilfield, Basrah Governorate, Southern Iraq

The biostratigraphy of the Early Cretaceous Mauddud Formation was studied in the Ratawi Oilfield, Basra Governorate, southern Iraq, using integrated borehole data set (core and cutting samples and well logs) in two drilled wells to analyze the biostratigraphy of the formation. One hundred eighty-three slides for both selected wells were investigated. The formation is composed of light grey dolomitized limestone and pseudo-oolitic creamy limestone with green to bluish shale. Three biozones were discriminated, these are: Orbitolina qatarica range zone; Orbitolina sefini range zone and Orbitolina concava range zone. The age of these biozones extends to include the Late Albian (Orbitolina qatarica); Late Albian-Early Cenomanian (Orbitolina sefini) and Early Cenomanian for (Orbitolina concava) zone. The fossils occurred are Conicorbitolina conica, Coral, gastropoda, Miliolids, Nezzazata , Neoiraqia convexa, orbitolina discoidia, Orbitolina kurdica, Spiroluculina sp., trocholina sp .

New Equations to Determine Shear Velocity from Compressional Velocity in Hf-2 Well, Halfaya Oil Field

The most important characters of the rock formations are shear and compression velocities, which are used to calculate elastic moduli. The geomechanical properties can be used to evaluate reservoir stability or to calibrate velocity and time/depth conversion, synthetic seismogram and other important applications. The aim of this study is to use the first order least square method to obtain an empirical equation to determine the shear velocity from compressional velocity for Mishrif, Rumaila, Ahmadi, and Mauddud formations in Hf-2 well. The obtained equations depend on sonic log and dipole shear sonic imager data of Hf-2 well and use Techlog software. The results from the obtained equations in comparison with those results of Green Castagna equation and measured data of dipole shear sonic imager of shear velocity for Mishrif, Rumiala and Mauddud formations. It is found from the comparison that the result is consistent each other’s. The consistent reflect the reality of shear waves values obtained in these formations. The comparison in Ahmadi formation also shows a consistent result for the obtained equations but it shows some differences from the dipole shear sonic imager and shear velocity reference values. The authors believed that the difference in some values of the Ahmadi Formation may be due to the high shale volume in comparison to the other formations.

Mixed carbonate-clastic reservoir characterization of the mid-Cretaceous Mauddud Formation (Albian), north Kuwait - Implications for field development

Mixed carbonate-clastic reservoir characterization of the mid-Cretaceous Mauddud Formation (Albian), north Kuwait - Implications for field development