ALNEELAIN UNIVERSITY THE GRADUATE COLLEGE Petrophysical Evaluation For Abu Gabra Formation-Muglad Basin, Neem K Area (Block 4) Using Wells Data A Dissertation Submitted to the Graduate College in Partial Fulfillment of the Requirements for the Master's Degree in Geophysics. By: Altayeb GassemAlbari Altayeb Ibrahim B sc. (Hons.) in Hydrogeology Alneelain University (2013). Supervisor: Dr. Mohamed Abdalhafeiz Ali Elyass Dec. 2019 بسم الله الرحمن الرحيم جمهورية السودان Republic of The Sudan جـــامــعــة النـيـــليــــن AL NEELAIN UNIVERSITY كلية الدراسات العليا The Graduate College Approval Page (To be completed after the college council approval) Name of candidate: Atayeb GassemAlbari Altayeb Ibrahim Thesis title: Petrophysical Evaluation for Abu Gabra Formation-Muglad basin, Neem K Area (Block 4) using wells data Degree Examination for: M.Sc. in Geophysics. 1. External Examiner Name………………………………………………………….......... Signature…………………..… Date…………………………… 2. Internal Examiner Name: ……………………………………………………………… Signature…………………..… Date…………………………… 3. Supervisor Name: ……………………………………………………………… Signature…………………..… Date…………………………… Abstract This study Petrophysical Evaluation for Abu Gabra formation – Muglad basin, Neem k subfield (Block 4) four wells data by using Interactive petrophysics IP. Interpretation of Shaly sand oil reservoirs is still evolving, with researchers to conduct a large number of studies to verify the effect of clay minerals on the conductivity of the reservoir through theoretical and experimental methods. In this study have been Petrophysical evaluated to Shaly sand reservoirs in the Neem k subfield by selecting one formation to know of the Petrophysical properties of the reservoir, it is formation of Abu Gabra. Determination of layers of clay and layers of sand in the well logs was done by using interpretation of gamma-ray records, records the electrical resistivity, density recordings, and Neutron recordings. The results obtained were effected by three major factors: porosity, the volume of clay in layers and water saturation of layers, experimental results show clear contrast in the average porosity (≥ 10%), average volume of clay (≤ 50%) and average water saturation (≤ 80%), was very compatible with characteristics of the reservoir. I الخﻻصة هذه الدراسه تمثل تقييم بتروفيزيائي لمتكون ابوجابره – حوض المجلد حقل نيم ك)مربع4(ﻻربعه ابار باستخدام برنامج انتراكتيف بتروفيزيك. تفسير خزانات الرمل الطيني النفطيه ﻻزالت تتطور مع اجراء الباحثين لعدد كبير من الدراسات للتحقق من تاثير المعادن الطينيه علي الموصليه الكهربيه للخزان من خﻻل الطرق النظريه والتجريبيه ،في هذه الدراسه تم تقييم بتروفيزيائي لخزانات الرمل الطيني في حقل نيم ك وذلك بتحديد متكون واحد لمعرفة الخصائص البتروفيزيائيه وهو متكون ابوجابره،تم تحديد الطبقات الطينيه والطبقات الرمليه بواسطة تفسير تسجيﻻت اشعة جاما ، تسجيﻻت المقاومه الكهربيه، وتسجيﻻت الكثافه ، وتسجيﻻت النيترون ، النتائج المتحصل عليها تم تقييمها عن طريق ثﻻث عوامل هي المساميه، حجم الطين في الطبقات ونسبة التشبع بالماء وقد اظهرت النتائج تفارق واضح في متوسط نسبة المساميه ، ومتوسط حجم الطين في الطبقات ، ومتوسط نسبة التشبع بالماء وقد كانت متوافقه جدا مع خصائص الخزان. II Dedication I dedicate this work to my parent, to my Wife, to my brothers and my sisters, to the soul of my grandmother. III Acknowledgements I wish to express my appreciation to my supervisor Dr. Mohamed Abdalhafiez Ali for his support and guidance through this project, Thanks and appreciation goes to the staff of the department of geophysics –Faculty of Petroleum and minerals at university ofAlneelain for their helping and encouragements. Special thanks and gratitude to Hasan Almalieh(OEPA) and Abd alzahier Mohiealdien (OEPA) for their supporting and helping during data interpretation, Sincere thanks are due to my colleagues at the Master program Batch 4 for their supports. IV Contents Title Page Abstract I Abstract in Arabic II Dedication V Acknowledgements IV Contents V List of Figures X List of Tables XIII CHAPTER ONE INTRODUCTION 1-1 Introduction 1 1-2 Physiography 3 1-3 Climate 3 1-4 Population 3 1-5 Location of study area 4 1-6 Accessibility 5 1-7 Problem Statement 5 1-8 Objective of the study 5 1-9 History of the Exploration 6 CHAPTER TWO REGEONAL GEOLOGY AND TECTONIC EVOLUTION 2-1 Introduction 8 2-2 Regional Geological Setting 9 2-3 Sudanese rift basins 15 2-3-1 West and Central African Rift Basins 15 2-3-2 Key Sudanese Rifts 16 V 2-3-3 Stress Field of Muglad Basin 17 2-3-3-1 Combined wrench and Normal Extension 19 Mechanism 2-3-3-2 Derivative Normal Extension Mechanism 20 2-3-3-3 Transtensional Mechanism 22 2-4 Stratigraphy of Muglad Basin 24 2-4-1 Precambrian-Jurassic 25 2-4-2 Cretaceous 25 2-4-2-1 Abu Gabra Formation 26 2-4-2-2 Bentiu Formation 26 2-4-2-3 Darfur Group 27 2-4-3 Tertiary 27 2-4-3-1 Amal Formation 28 2-4-3-2 Nayil and Tendi Formations 28 CHAPTER THREE METHODS OF IVESTIGATION 3-1 Introduction 29 3-2 Log Interpretation 30 3-3 Zoning 32 3-3-1 SP 32 3-3-1-1 SP Theory 32 3-3-1-2 SP uses 35 3-3-1-3 Rw from the SP 35 3-3-1-4 SP borehole Effects 38 3-3-2 Gamma Ray Principles 39 3-3-2-1 GR Technique 39 3-3-2-2 GR Uses 40 3-3-2-3 GR parameters 42 3-3-2-4 GR applications 42 3-3-2-5 GR Limits 43 VI 3-3-3 Caliper 46 3-3-4 Lithology and Porosity Tools 47 3-3-4-1 Neutron Tool 47 3-3-4-1-1 Hydrogen Index 48 3-3-4-1-2 Thermal Neutron Parameters 49 3-3-4-1-3 Interpretation and Uses 50 3-3-4-2 Density Tool 50 3-3-4-2-1 Density Parameters 51 3-3-4-2-2 Interpretation and Uses 52 3-3-4-2-3 The Porosity from Density 53 3-3-4-3 Sonic Tool 53 3-3-4-3-1 Sonic Porosity Equation 54 3-3-4-3-2 Sonic Parameters 55 3-3-5 Electrical Resistivity Logs 56 3-3-5-1 Resistivity Theory 56 3-3-5-2 Resistivity Theory 2 57 3-3-5-3 Resistivity Model 58 3-3-5-4 Mud Resistivities 59 3-3-5-5 Normal and Lateral Tools 59 3-3-5-5-1 Laterolog Principle 61 3-3-5-5-2 Tool Types 62 3-3-5-5-3 Azimuthal Laterolog principle 62 3-3-5-5-4 Laterologs borehole effect 63 3-3-5-5-5 Azimuthal Laterolog corrections 63 3-3-5-5-6 Bed Correction 66 3-3-5-5-7 Laterolog Applications 67 3-3-5-5-8 Laterolog Limits 68 3-3-5-6 Microresistivity Tool 68 3-3-5-6-1 Uses of Microresistivity Tool 68 3-3-5-6-2 MSFL Borehole Corrections 68 3-4 Saturation Computation 69 VII 3-4-1 Basics 1 69 3-4-2 Basics 2 70 3-4-3 Other Relationships 71 CHAPTER FOUR PETROPHYSICAL EVALUATION 4-1 introduction 73 4-2 acquiring raw data from logs 74 4-2-1 correlation between logs 74 4-2-2 zone selection 74 4-3 petrophysical evaluation 76 4-3-1 reservoir and lithology determination 77 4-3-1-1 Reservoir Identification 77 4-3-1-2 lithology determination 80 4-3-1-2-1 shale volume content 80 4-3-1-2-1-1 shale content from sp log 80 4-3-1-2-2 shale content from the gamma ray log 80 4-3-1-3 porosity esitmation 85 4-3-1-3-1 quantitative interpertation from porosity logs 85 4-3-1-3-2 the porosity from the neutron/density crossplot 86 4-3-2 saturation determenatin 90 4-3-2-1 determination of water saturation 90 4-3-2-2 determination of hydrocarbon saturation 92 4-4 petrophysical cut-off values determination 95 4-4-1 clay volume cutoff 95 4-4-2 porosity cutoff 96 4-4-3 water saturation cutoff (Sw cutoff) 97 4-4-4 reservoir summation and interpretation of results 98 VIII CHAPTER FIVE CONCLUSION AND RECOMMENDATION 5-1 Conclusion 113 5-2 Recommendations 114 5-3 References 115 5-4 Appendix 121 IX LIST OF FIGURES Title Page 1-1 Location map for the Muglad basin 2 1-2 Location map for the study area Neem K 4 2-1 Gondwana, showing location of cratons and Pan-African 9 belts in West and Central Africa and adjacent regions 2-2 Tectonic models of the West and Central African Rift 11 System from Fairhead (1988). 2-3 Tectonic Development of West and Central Africa. 13 2-4 Diagram showing Sudanese rift system and its relationship 17 to adjacent structures. 2-5 Sketches of Paleogeologic evolution of WCARS 18 (Genik,1993). 2-6 Regional Stress field during Early Cretaceous, (from 20 Mohamed Y et al, 1999, Bosworth W., 1991, Rene Guiraud et al, 1992, RIPED, 2001). 2-7 Regional Stress field during Late Cretaceous, (from 21 Mohamed Y et al, 1999, Bosworth W., 1991, Rene Guiraud et al, 1992, RIPED, 2001) 2-8 Regional Stress field during late Eocene to recent, (from 23 Mohamed Y et al, 1999, Bosworth W., 1991, Rene Guiraud et al, 1992, RIPED, 2001). 2-9 Composite Column of Muglad Basin (from Schull 1988). 24 3-1 Explaining Why Run Logs (Log interpretation can provide 29 answers to questions on). 3-2 Sketch show the reservoir and well. 30 3-3 Explain sp curve and shaleline. 34 3-4 chart sp-1 to find ratio Rmfe/Rwe 36 3-5 Chart sp-2 to determine RW. 37 3-6 SP deflection , shows the beds as distinct from each ot9her. 38 3-7 Shows the radioactive series (Potassium, Thorium, 39 Uranium).