Basic PPFG_Kuliah Tamu Rev 0.1 fakultas teknik

geology

1. Ahmad Humam Fanani, S. T. Educational Background ABOUT THE SPEAKER S1 Geological Engineering (2016-2020) Fakultas Teknik Universitas Mulawarman Organizational Milestone Professional Career Vice Chairman (2017-2018) HMTG – Universitas Mulawarman Chairman (2018-2019) SM IAGI – Universitas Mulawarman Member (2018-2019) Pengda IAGI – Kalimantan Timur Apprentice Pore Pressure Analyst (2021) PHI Zona 8 – PHM Wellsite Geologist (2021 – 2023) PHI Zona 9 – PHSS & PEP A5 Pore Pressure Analyst (2023 – Now) PHI Zona 9 – PHSS & PEP A5 Up to 3 years experience in O&G industry as an Operation Geologist (Formation Evaluation, Subsurface Data Acquisition, Risk Mitigation)

2. BASIC PORE PRESSURE & FRACTURE GRADIENT WOPDM - PPFG Team

3. Gulf of Mexico, 2010 Sidoarjo, 2006 Piper Alpha, 1988 Texas GEOLOGICAL HAZARD RELATED TO PPFG Source : Wikipedia

4. WHY WE NEED TO PPFG ANALYSIS? Safety concer ns while drilling and/or well intervention Well design & completion Drilling window Drilling hazards mitigation Geological evaluation Hydrocarbon accumulation Sand Distribution Formation evaluation data acquisitions Geomechanic evaluation Cost effectiveness

5. OUTLINE PRESENTATION Pore Pressure Concept Geological hazard related to PPFG Standard unit measurements Datum Reference Pore Pressure & Regimes Overburden Pressure Concept Overburden Stress / Gradient Calculation Examples Fracture Pressure Concept Stress Model Effective Stress Fracture Pressure/Gradient Wellbore Stability Concept Wellbore Stress Wellbore Failure Managing Wellbore Failure Basic Understanding Overpressure Generating Mechanism Overpressure Definition Overpressure Driving Mechanism Loading (Disequilibrium Compaction) Non-Loading Hydrocarbon Generation Dynamic Pressure Transfer P Res and P S hale Relationship

6. Pore Pressure Concept

7. How to feel the Stress or Pressure?? 10 Kg 1 MPa = 10 bar 1 cm 2 1 Kg 1 bar = 14.5 psi 1 cm 2 0.3 MPa = 3 bar = 43 psi 1 cm 2 What is the air for car tires? 30 – 35 psi

8. STANDARD UNIT MEASUREMENT

9. DATUM REFERENCE RT / RKB RT / RKB air gap FWL MSL Elevation Sea bed Water Depth GL TVD TVDSS TVDSS TVD ONSHORE OFFSHORE FWL GL RT / RKB Elevation MSL RT / RKB air gap Sea bed Water Depth ONSHORE OFFSHORE TVD = Reference for measurement & calculation TVDSS = Reference for correlation ( MW, ECD, PT, LOT & Drilling Event) (Pore Pressure & Overburden Gradient)

10. Force (F) Pressure (P) = Area (A) PHYSICAL PO INT OF VIEW F = N A = m² P = bar, psi & Pa PRESSURE is force per unit area PRESSURE Scalar Domain – in fluid (Shear Strength* = 0) S TRESS Tensor Domain – in solid (Shear Strength* ≠ 0) PRESSURE / STRESS “Pressure of the fluid where contained in the pore spaces ” F ORMATION PRESSURE ? “ P ORE PRESSURE” Area Field units : bar, psi or MPa *Shear Strength = the maximum stress that a material can withstand before its starting to failure Normal Condition VERTICAL STRESS ( σ ) Water escape VERTICAL STRESS ( σ )

11. NORMAL COMPACTION TREND Compaction (mechanical): in normal condition, compaction (in shale) will reduce the porosity and thickness. The deeper, the lower porosity. The deeper, the greater effective stress. For argillaceous rocks Shale Sonic NCT Top OVP Depth In order to evaluate abnormal pressures it is necessary to define a normal compaction trend for reference. The slope is influenced by : Mineralogy and non argillaceous material content Sedimentation rate Geothermal gradient = F e - cZ (compaction factor) All NCT’s are derived from the Hubbert & Rubey law: Normal Condition VERTICAL STRESS ( σ ) Under Compaction Water unable / less to escape VERTICAL STRESS ( σ ) VERTICAL STRESS ( σ ) VERTICAL STRESS ( σ )

12. MUARA TANJUNG UNA ANGGANA North South TANJUNG UNA MUARA ANGGANA Anggana NCT: Mudline sonic : +/- 145 – 152 us/ ft Lambda : 0.25 – 0.34 Tanjung Una NCT: Mudline sonic : +/- 140 – 145 us/ ft Lambda : 0.25 – 0.33 Muara NCT: Mudline sonic : +/- 133 – 140 us/ ft Lambda : 0.25 – 0.30 *NCT trend relatively higher from southern to northern structure, yet still relatively close each others NCT & Erosional Intensity NORMAL COMPACTION TREND Compaction is the process by which sediment progressively lose the porosity due to the effects of overlying sediment (burial). It will increasing the effective stress. Workshop_Basic PPFG Analysis_02 Aug 2022 12

13. PRESSURE & REGIMES GRADIENT PSI O VERPRESSURE SUB- PRESSURE NORMAL PRESSURE (HYDROSTATIC) PP < NP PP = NP PP > NP W ater level at surface W ater level above surface W ater level below surface 1 2 3 DEPTH PRESSURE P = ρ x g x h Unit : P = Pressure (psi) Ρ = Density fluid (g/cc) g = Acceleration of Gravity (m/s2) h = Height or Depth (m or ft ) A h Water Level (at surface)

14. Depleted Reservoir The depleted reservoir is the pressure depletion in reservoir due to the production activity in the development area of oil and gas field. The pressure depletion value can very low far below the normal hydrostatic pressure depend on the production time, rate and number of wells (reservoir drainage area). The over depleted reservoir often causes numbers of drilling problems during further development of the mature oil and gas field, such as severe losses, stuck pipe risk due to differential pressure sticking, high vertical pressure gap between Clay pressure and reservoir pressure causing mechanical breakout problem, etc. Lateral drainage discharge (shoulder effect) The shoulder effect is the pressure depletion of the rock layer series that connected to the lateral discharge area. The commonest causes is the reservoir outcropping at a lower altitude than the elevation at which it was penetrated during drilling This explains why such pressure anomalies are so frequently encountered in mountainous areas. The position of the water table in relation to the land surface is also a cause of subnormal pressure, especially in arid areas. The reservoir is said to be subnormal pressured if its pore pressure is lower than the normal hydrostatic pressure. Abnormal Formation Pressure - Negative Anomaly (Subnormal Pressure)

15. Overpressure is the pore pressure that excess over the normal hydrostatic pressure. When the overpressure is much smaller than the vertical effective stress, the overpressure is said to be ‘low’. when it approaches the vertical effective stress, it is said to be ‘high’ or ‘hard’. Basic terminology of stress (Agus M. Ramdhan , doctoral thesis, pg. 30) The interval a–b is an interval of low overpressure, the interval b–c is a transition to hard overpressure zone, and the interval below point ‘c’ is a zone of high overpressure. Abnormal Formation Pressure - Positive Anomaly (Overpressure) -Drilling a reservoir below its intake level (Artesian well) Artesian Well Artesian well is overpressure due to the intake point (outcrop) of an aquifer drilled is situated at a higher altitude than the well site. Hydrocarbon Buoyancy Another example is the overpressure due to buoyancy at different fluid density interface (in this case, formation water and hydrocarbon). 15

16. Overburden Pressure Concept

17. Overburden Stress Overburden stress is the pressure exerted by the weight of overlying sediments. I ncluding : sea water + Matrix + fluids into porous medium. σ = r b * g * h Unit : σ = Overburden stress (psi) Overburden stress (kg/cm 2 ) ρ b = average bulk density include pore fluid ( gr /cm 3 ) ρ m = matrix density ( gr /cm 3 ) ρ f = fluid density ( gr /cm 3 ) h = Z/ msl g = gravitational constant Fluid + Rock Weight of EMW TVD TVD EMW cumulative S OBG air gap cumulative S OBG sea water S OBG expressed in EMW RT RT r b = r m *(1-ϕ) + r f * ϕ σ = r b * ( h/10 )

18. OVERBURDEN CALCULATION EXAMPLE 18

19. Fracture Pressure Concept

20. WORLD STRESS MAP Represent the orientation of maximum horizontal stress and stress regimes

21. 21 PRINCIPAL STRESSES / STRESS MODEL PORE PRESSURE & PRINCIPAL STRESSES Fracture pressure is the amount of pressure required to initiate a fracture hydraulically. It usually expressed as a gradient with the common units being psi/ft or ppg. Fracture occurred when the minimum compressive stress and tensile strength of the rock are exceeded by the external pressure. In the subsurface they are 3 principal stresses acting on rocks: •Total vertical stress ( Sv ): comes from overburden/litho-static pressure. •Minimum horizontal stress ( Sh min): can be measured by leak off test (LOT) •Maximum horizontal stress (SH max): is generally poorly known, but is orientation can be estimated from borehole breakout and drilling induced fracture. FRACTURE PRESSURE (Baker Hughes, 2018) FAILURE MECHANISM

22. FRACTURE PRESSURE FP = ( OBG - PP ) x (PR/(1-PR)) + PP Also called Minimum Horizontal Stress Limit of the rock strength according to the pressure As also practical limit of overpressure. FG Calibration Data : ECD loss while drilling at depleted lithology Leak Off Test (LOT) *Fracture pressure calculated by Eaton formula P ( sg ) TVD ss (m) Pp Sv =  v Mudline  h = FCP LOP  FP FBP F F This point is the limit of rock strength  t he weakest point is related to the depleted reservoir  t he lower P = Lower FP FP = Fracture pressure (SG) OBG = Overburden stress (SG) PP = Pore Pressure (SG) Ki = Effective Stress Ratio = Poisson Ratio

23. EFFECTIVE STRESS HYDRAULIC TEST/ LEAK OFF TEST (LOT) MW and / or ECD > Fracture Gradient Secondary porosity influence Unconsolidated formation 23

24. Hydraulic Test Time Well Pressure increases linearly in open hole Pressure increase and microfractures occur. Star t End Start End Shmin SH Pressure decreases as fractures propagate Start End Shmin SH Fracture stops Start SH End Shmin Shmin Shmin Wellbore Pressure = Shmin Fractures are closed: (Wellbore Pressure < Shmin ) Downhole Pressure Pump – in (constant rate) Shut -in Bleed-off Breakdown Pressure/ Fracture Initiation Pressure Fracture Propagation Pressure Instantaneous Shut In Pressure Fracture Closure Pressure LOP FCP = Shmin 3 2 1 FBP/FIP Leak Off Pressure 1 Pressure < LOP 2 LOP < Pressure < FBP/FIP 3 Pressure > FBP/FIP 4 4 Pumping stopped, tangent to curve marks Fracture Closure Pressure (FCP)

25. Wellbore Stability Concept

26. 26 WELLBORE STRESSES Before drilling the well, the rock was in an equilibrium condition under the combination effects of in-situ stress, pore pressure and rock strength. The influenced stresses known as Far Field Stresses Drilling mud induced the previous condition to create new equilibrium system around the wellbore with local stress system / near wellbore. The local stress system around the wellbore known as near / wellbore stresses .

27. 27 (Total S.A., 2015) WELLBORE STRESSES (WELL TRAJECTORY)

28. 28 UTM, 2015 WELLBORE STRESSES Hoop Stress Axial Stress Radial Stress Tensile failure due to negative hoop stress Near wellbore stress & shear stress

29. 29 WELLBORE STRESSES MEASUREMENT (CALIPER LOG) Breakout Wellbore enlargements caused by stress-induced failure of a well occur 180deg apart. In vertical wells breakout occur at the azimuth of minimum horizontal stress ( Shmin ) and has a consistent orientation within a given well or far field. Washout Complete failure of the borehole in which all of the arm read larger than the bit diameter – no orientation. Keyseat Assymetrical notching of the well caused by mechanical wear of the borehole at the top or bottom. Borehole caliper measurement

30. 30 WELLBORE STRESSES MEASUREMENT (IMAGE LOG & LAB TEST) Shear failure breakout observed during laboratory testing on a large core sample Azimuth Orientation Core Sample

31. 31 WELLBORE FAILURE (BREAKOUT & TENSILE) (Baker Hughes, 2018)

32. 32 WELLBORE FAILURE (Baker Hughes, 2018)

33. 33 MANAGING WELLBORE FAILURE (Zhang et al., 2008) Lost circulation happened when the mud pressure (MW and/or ECD) is higher than fracture gradient (FG) Wellbore stability issue happen when the mud pressure insufficient or even lower than pore pressure

34. Underpressure is the pressure lower than normal hydrostatic Overpressure Overpressure is the amount of pressure above the normal hydrostatic pressure. It is also called abnormal pressure , excess pore pressure and geopressure . O H O Pressure that higher than normal hydrostatic  Is the overpressure H The max height of fluid (water) on surface  Is the normal hydrostatic 34 Day 1_Basic Pore Pressure, Stress Model and Overpressure Generating Mechanisms

35. OVERPRESSURE DRIVING MECHANISM OVERPRESSURE is the anomaly of formation pressure which above the normal hydrostatic pressure. OVERPRESSURE STRESS RELATED Fluid Compression Disequilibrium Compaction Tectonic Compression THERMAL Fluid Compression Hydrocarbon Generation Aquathermal Pressuring DYNAMIC TRANSFER Transference Vertical / Lateral Transfer Various Effects Fluid Expansion HC Column Uplift Osmosis OTHER Mineral Diagenesis CHEMICAL 1 st Order 3 rd Order 2 nd Order or less frequent

36. ( Ramdhan and Goulty , 2011) LOADING OVP GENERATING MECHANISM Normal Condition VERTICAL STRESS ( σ ) Water escape Under Compaction Water unable / less to escape VERTICAL STRESS ( σ ) VERTICAL STRESS ( σ ) VERTICAL STRESS ( σ ) DISEQUILIBRIUM COMPACTION (UNDER COMPACTION) Transformation of rocks / sediments which failed to compact which made fluid / water can’t escape from the pore space. Causes : Dewatering fluid rate is slower than burial rate (increasing vertical stress / overburden) Constant effective stress & porosity v = p + σ v' Under Compaction v = p + σ v' Normal Condition p = Pore pressure σv ’ = Effective stress v = Vertical Stress = Increase = Constant σ v' p v σ v' p v STRESS RELATED

37. UNLOADING OVP GENERATING MECHANISM LOAD TRANSFER – THERMAL ( Ramdhan and Goulty , 2011) UNLOADING Overpressure generating mechanism which influenced by transfer load to fluid in the pore space. Causes : Mineral diagenesis (related to diagenetic factors) > released fluid (fluid expansion) Hydrocarbon generation (kerogen to HC) Decreasing effective stress & increasing porosity Unloading Mineral diagenesis released fluid into pore space VERTICAL STRESS ( σ ) VERTICAL STRESS ( σ ) σ v' p v v = p + σ v' Unloading p = Pore pressure σv ’ = Effective stress v = Vertical Stress = Increase = Decrease = Constant

38. Geological processes of fluid expansion : hydrocarbon generation. Kerogen to gas: Could produce overpressure as high as 11.020 psi . Oil generation: Could produce overpressure as high as 6245 psi . 1 Load bearing Kerogen 2 2 Initial Effective Stress 3 Effective Stress after unloading 3 1 UNLOADING OVP GENERATING MECHANISM Hydrocarbon Generation

39. UNLOADING OVP GENERATING MECHANISM DYNAMIC TRANSFER PRESSURE TRANSFER Overpressure generating mechanism which influenced by transfer of pressure due to fluid density differences within column. Causes : Difference density between fluid > gas, oil & water Availability of path for pressure transfer (pore connectivity, fracture or fault) P hc = ( ρw – ρhc ) x g x h Unit : P = Pressure (psi) Ρ = Density fluid (g/cc) g = Acceleration of Gravity (m/s2) h = Height or Depth (m or ft ) WELL A WELL B WELL A WELL B WELL A WELL B WELL A WELL B

40. Causes of Overpressure: Ranking Main frequently causes of overpressure : Disequilibrium Compaction ( Mech anical Stress) Organic Matter Transformation Lateral pressure transfer and hydrodynamism Secondary or less frequently significant : Hydrocarbon buoyancy Tectonic Compression ( Uplift ) Lateral Tectonic Stress

41. P Res and P Shale Relationship Reservoir pressure ( P Res ) can be measured.  MDT ( wireline log), DST, etc. Shale pressure ( P Shale ) can be modeled based on indirect indicators of porosity evolution.  It can not be measured directly. Reservoir Pressure There are 3 relationship of P res and P shale : P res = P shale  thin, isolated, poor drainage reservoir ( closed system ). P res < P shale  good drainage, depleted reservoir ( open system ). P res > P shale  buoyancy effect, hydrocarbon column ( closed system ).

42. Wireline Engineer : pressure test and fluid analysis Pressure Time Formation Pressure P final build-up ~ P res Reservoir Pressure ( P Res ): System Winch man : maintain and operate control device Operator : makeup tools and calibrations

43. Shale Pressure ( P Shale ): Prediction

44. CP PLAN 9-5/8” @6 5 0’ TVDSS WELL TD PLAN @4520’ TVDSS Section 8-1/2 ” Targets : F3120-04 @680’ TVDSS (Est Current Pressure 8.8ppg ) F3200-11 @849’ TVDSS (Est Current Pressure 9.1ppg ) I3020-08 @2418’TVDSS (Est Current Pressure 8.2ppg ) I3100-03 @2566’ TVDSS (Est Current Pressure 8.7ppg ) J3400-01 @4393’ TVDSS (Est Current Pressure 8.7ppg ) Surrounding Well Issues : Loss (WELL-051, WELL 199, WELL-305 & WELL-967) Kick while performed checkshot (WELL-108) Connection Gas (WELL-199 & WELL 305) Potensial Losses : Potensial Loss 1 (Loss history WELL- 051, WELL -199, WELL- 305 & WELL -967 ) Potensial Loss 2 (FG min 12.30ppg) Potensial Loss 3 (FG min 12.50ppg) Overpressure : Not penetrated POT LOSS 1 POT LOSS 2 POT LOSS 3 Est. BHT 92degC (Ref Temp RFT WELL -967) PORE PRESSURE & FRACTURE GRADIENT PROFILE PREDICTION

45. THANK YOU “ Everything is Expensive and Must be Planned Well in Advance. Pore Pressure and Fracture Prediction is a serious concern as it has an impact on safety and costs ”

46. (TOTAL S.A., 2015) PORE PRESSURE DETECTION WHILE DRILLING