scholarly journals Prediction of Formation Pressure Gradients of NC98 Field-Sirte Basin-Libya

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Ahmed Tunnish ◽  
Mohammed Nasr ◽  
Mahmoud Salem
Keyword(s):  
Pore Pressure ◽  
Well Logging ◽  
Pressure Gradients ◽  
Formation Pressure ◽  
Empirical Methods ◽  
Fracture Pressure ◽  
Significant Step ◽  
Sirte Basin ◽  
Formation Pore Pressure ◽  
Oil Company

The prediction of formation pore pressure and fracture pressure gradients is a significant step towards the drilling plan. In this study, the formation pressures of twelve wells from NC98 field-Sirte Basin (Waha Oil Company) were calculated by employing empirical methods, Eaton’s equations, that depend on the real drilling and well-logging data. Regarding the results, the normal pore pressure in the NC98 field in Sirte basin is 0.437 Psi/ft, and it is extending from the top of the wells in the investigated area to 7,000 ft. A subnormal to normal pore pressure zone is noticed in the interval of 7,000 ft. to 9,000 ft. Then, slightly subnormal to somewhat abnormal (overpressure) region is seen from 9,000 ft. to 11,200 ft. Beyond to that depth and down to the top of the reservoir, the overpressure zone was clearly observed. Based on the results, the casing setting depth and the equivalent mud weight were simply determined for the area of study.

scholarly journals Post Drill Pore Pressure Prediction for Geo-hazard Assessment of Offset Wells in Hamoru Field

2020 ◽  
Vol 17 (2) ◽  
pp. 97-103
Author(s):  
A. Ogbamikhumi ◽  
O.M. Hamid-Osazuwa ◽  
E.A. Imoru
Keyword(s):  
Pore Pressure ◽  
Hazard Assessment ◽  
Seismic Data ◽  
Field Analysis ◽  
Well Logs ◽  
Formation Pressure ◽  
Pore Pressure Prediction ◽  
Pressure Regime ◽  
Formation Pore Pressure ◽  
Subsurface Formation

Understanding the distribution and variation of subsurface formation pressure is key to preventing geo-hazards associated with drilling activities such as kicks and blow out. To assess and prevent such risk in drilling offset wells in the Hamoru field, prediction of pore pressure was done to understand the pressure regime of the field using well logs in the absence of seismic data. Two commonly used methods for formation pressure prediction; Bower’s and Eaton’s methods were adopted to predict pore pressure and determine the better of the two methods that will be more suitable for the field. The cross-plot of Vp against density disclosed that compaction disequilibrium is the prevalent overpressure mechanism. The prediction of Pore pressure with Eaton’s method gave results comparable to the acquired pressure in the field, typical of what is expected when compaction disequilibrium is the dominant overpressure mechanism. Since the result of Bower’s method over estimated formation pressure, Eaton’s method appears to be the better choice for predicting the formation pore pressure in the field. Analysis of the predicted pore pressure reveals the onset of overpressure at depth of 2.44 km. The formation pressure gradient ranges from 10.4 kPa/m to 15.2 kPa/m interpreted as mild to moderately over pressure. Keywords: Geohazard, over-pressure, Eaton’s method, Bower’s method, normal compaction trend

Predicting Formation Pore-Pressure from Well-Log Data with Hybrid Machine-Learning Optimization Algorithms

2021 ◽  
Author(s):  
Mohammad Farsi ◽  
Nima Mohamadian ◽  
Hamzeh Ghorbani ◽  
David A. Wood ◽  
Shadfar Davoodi ◽  
...  
Keyword(s):  
Machine Learning ◽  
Pore Pressure ◽  
Optimization Algorithms ◽  
Well Log ◽  
Log Data ◽  
Hybrid Machine ◽  
Formation Pore Pressure

Determining Fracture Pressure Gradients From Well Logs

1973 ◽  
Vol 25 (11) ◽  
pp. 1259-1268 ◽  
Author(s):  
R.A. Anderson ◽  
D.S. Ingram ◽  
A.M. Zanier
Keyword(s):  
Well Logs ◽  
Pressure Gradients ◽  
Fracture Pressure

scholarly journals Abnormal Pressure Distribution of Tertiary age formations in Middle & South Iraqi Oil Fields

2021 ◽  
Vol 7 (4) ◽  
pp. 46-63
Author(s):  
Dr. Faleh H. M. Almahdawi ◽  
Dr. Kareem A. Alwan ◽  
Ahmed K. H. Alhusseini
Keyword(s):  
Hydrostatic Pressure ◽  
Pressure Distribution ◽  
Oil Fields ◽  
Formation Pressure ◽  
Abnormal Pressure ◽  
Drilling Operations ◽  
South Of Iraq ◽  
Abnormal Formation Pressure ◽  
Formation Pore Pressure ◽  
Pore Pressure Gradient

Prediction of formation pore pressure gradient is a very important factor in designingdrilling well program and it help to avoid many problems during drilling operations such as lostcirculation, kick, blowout and other problems.In this study, abnormal formation pressure is classified into two types; abnormal highpressure (HP) and abnormal low pressure (LP), therefore any pressure that is either above orbelow the hydrostatic pressure is referred to as an abnormal formation pressure.This study concerns with abnormal formation pressure distribution and their effect ondrilling operations in middle & south Iraqi oil fields. Abnormal formation pressure maps aredrawn depending upon drilling evidence and problems.Three formations are considered as abnormal formations in the region of study, theseformations geologically existed in Tertiary age and they from shallower to deeper are: LowerFars, Dammam and Umm Er Radhuma, Formations. The maps of this study referred to eitherhigh formations pressure such as (Lower Fars and Umm Er Radhuma) or the low formationspressure such as (Dammam) in middle and south of Iraq. Finally these maps also suggested andshowed the area, where no field is drill until now, which may behave as high, low and normalformation pressure for every formation understudy.

Possible Reason of the Dependence of an Apparent Permeability on the Pressure Gradient at low Flow Rates in Laboratory Study

2021 ◽  
Author(s):  
Nikolay Baryshnikov ◽  
Evgeniy Zenchenko ◽  
Sergey Turuntaev
Keyword(s):  
Pressure Gradient ◽  
Pore Pressure ◽  
Pore Space ◽  
Low Flow ◽  
Pressure Gradients ◽  
Apparent Permeability ◽  
Flow Rates ◽  
Rock Samples ◽  
Pore Pressure Gradient ◽  
Filtration Properties

<p>Currently, a number of studies showing that the injection of fluid into the formation can cause induced seismicity. Usually, it is associated with a change in the stress-strain state of the reservoir during the pore pressure front propagation. Modeling this process requires knowledge of the features of the filtration properties of reservoir rocks. Many researchers note the fact that the measured permeability of rock samples decreases at low pressure gradients. Among other things, this may be due to the formation of boundary adhesion layers with altered properties at the interfaces between the liquid and solid phases. The characteristic thickness of such layer can be fractions of a micron, and the effect becomes significant when filtering the fluid in rocks with a comparable characteristic pore size. The purpose of this work was to study the filtration properties of rock samples with low permeability at low flow rates. Laboratory modeling of such processes is associated with significant technical difficulties, primarily with the accuracy limit of measuring instruments when approaching zero speed values. The technique used by us to conduct the experiment and data processing allows us to study the dependence of the apparent permeability on the pore pressure gradient in the range of 0.01 MPa/m, which is comparable to the characteristic pressure gradients during the development of oil fields. In the course of the study, we carried out laboratory experiments on limestone core samples, during which the dependencies of their apparent permeability on the pore pressure gradient were obtained. We observed a significant decrease in their permeability at low flow rates. In the course of analyzing the experimental results, we proposed that a decrease in apparent permeability may occur due to the effect of even a small amount of residual gas in the pore space of the samples. This has been confirmed by additional experiments. The possibility of clogging of core sample pore space must be considered when conducting when conducting laboratory studies of the core apparent permeability.</p>

Significant Performance Improvement with MPD in HPHT Narrow Drilling Window Campaign in the North Sea

2021 ◽  
Author(s):  
Babar Kamal ◽  
Abdul Saboor ◽  
Graeme MacFarlane ◽  
Frank Kernche
Keyword(s):  
Precise Determination ◽  
Lessons Learned ◽  
Overburden Pressure ◽  
The North ◽  
Fracture Pressure ◽  
Open Hole ◽  
Infill Drilling ◽  
Significant Performance ◽  
And Performance ◽  
Formation Pore Pressure

Abstract Significant depletion in reservoir pressure, huge uncertainties in pore and fracture pressure, high overburden pressure on top of reservoir, Narrow Mud Weight Window (NMWW) and Partial/Total losses whilst entering the reservoir made these HPHT (High Pressure High Temperature) wells conventionally un-drillable. Due to these substantial challenges these wells were considered not only costly but also carry a high probability of failure to reach well TD (Total Depth). MPD (Managed Pressure Drilling) is a safer and more effective drilling technique as compared to conventional drilling, especially in wells with NMWW and downhole hazards. The precise determination and dynamic downhole pressure management was imperative to complete these wells without well control incidents. The Constant Bottom Hole Pressure (CBHP) variant in combination of automated MPD system was deployed with a mud weight statically underbalanced while dynamically managed above formation pore pressure to minimize the overbalance across the open hole. MPD enabled the operator to efficiently navigate Equivalent Circulation Density (ECD) through the pore and fracture pressure window, allowed significant improvements throughout the entire campaign. This paper discusses the challenges faced during the last three wells drilled in the campaign which includes equipment issues, commissioning delays, losses whilst drilling, Managed Pressure Cementing (MPC), 7" drill-in-liner and plugged/blocked lines due to weather and mud conditions. The paper describes HPHT infill drilling experience, specific techniques, practices as well as lessons learned from each well during the campaign were implemented to address challenges and to improve performance. The MPD system commissioning was optimized by repositioning the lines which saved significant critical rig time. The blowdown points were added on the lines that were not operational continuously therefore a procedure was developed for flushing to avoid plugging. Optimized drilling strategy was also developed where MW was further reduced to avoid losses as observed in previous wells and CBHP was maintained by manipulating Surface Back Pressure (SBP) from surface. This paper also discusses continuous improvements /upgrades in MPD operating software which assisted the operator in accurate monitoring of flow, SBP and BH-ECD to save significant rig cost in terms of invisible Non-Productive Time (NPT). MPD is a drilling enabler and performance enhancer which saved 80 days of Authorization for Expenditure (AFE) on this challenging HPHT campaign.

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