scholarly journals Identification of Geo – Hazard Using Pore Pressure Analysis in ‘MAC’ Field, Niger Delta

2021 ◽  
Keyword(s):  
Pore Pressure ◽  
Gamma Ray ◽  
Pressure Data ◽  
Abnormal Pressure ◽  
Pore Pressure Prediction ◽  
Wireline Logs ◽  
Formation Pore Pressure ◽  
Resistivity Log ◽  
Gamma Ray Log ◽  
Pressure Analysis

Identification of geo-hazard zones using pore pressure analysis in ‘MAC’ field was carried out in this research. Suite of wireline logs from four wells and RFT pressure data from two wells were utilized. Lithologic identification was done using gamma ray log. Resistivity log was used to delineate hydrocarbon and non-hydrocarbon formations. Well log correlation helps to see the lateral continuity of the sands. Pore pressure prediction was done using integrated approaches. The general lithology identified is alternation of sand and shale units. The stratigraphy is typical of Agbada Formation. Three reservoirs delineated were laterally correlated. Crossplot of Vp against density (Rho) colour coded with depth revealed that disequilibrium compaction is the main overpressure generating mechanism in the field. Prediction of overpressure by normal compaction trend was generated and plot of interval transit time against depth show that there is normal compaction from 250m to about 1700 m on MAC-01, but at a depth of about 1800m, there was abnormal pressure build up that shows the onset of overpressure. A relatively normal compaction was observed on MAC-02 until a depth of about 2100m where overpressure was suspected. The prediction of formation pore pressure using Eaton’s and Bower’s method to determine the better of the two methods to adopt for pore pressure prediction shows that the pore pressure prediction using Eaton’s method gave a better result similar to the acquired pressure in the field. Hence Eaton’s method appears to be better suited for formation pore pressure estimation in ‘MAC’ field. The validation of the pore pressure analysis results with available acquired pressure data affirmed the confidence in the interpreted results for this study.

scholarly journals Real-Time Pore Pressure Detection: Indicators and Improved Methods

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Jincai Zhang ◽  
Shangxian Yin
Keyword(s):  
Real Time ◽  
Pore Pressure ◽  
Wellbore Instability ◽  
Abnormal Pressure ◽  
Measurement While Drilling ◽  
Pore Pressure Prediction ◽  
Pressure Indicators ◽  
Background Gas ◽  
Mud Logging ◽  
Improved Methods

High uncertainties may exist in the predrill pore pressure prediction in new prospects and deepwater subsalt wells; therefore, real-time pore pressure detection is highly needed to reduce drilling risks. The methods for pore pressure detection (the resistivity, sonic, and corrected d-exponent methods) are improved using the depth-dependent normal compaction equations to adapt to the requirements of the real-time monitoring. A new method is proposed to calculate pore pressure from the connection gas or elevated background gas, which can be used for real-time pore pressure detection. The pore pressure detection using the logging-while-drilling, measurement-while-drilling, and mud logging data is also implemented and evaluated. Abnormal pore pressure indicators from the well logs, mud logs, and wellbore instability events are identified and analyzed to interpret abnormal pore pressures for guiding real-time drilling decisions. The principles for identifying abnormal pressure indicators are proposed to improve real-time pore pressure monitoring.

scholarly journals Pore Pressure Prediction Using Artificial Neural Network Based On Logging Data

2020 ◽  
Vol 4 (1) ◽  
pp. 33
Author(s):  
RAKA SUDIRA WARDANA ◽  
Meredita Susanty ◽  
Hapsoro B.W
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Pore Pressure ◽  
Direct Measurement ◽  
Empirical Models ◽  
Measurement Methods ◽  
Pressure Data ◽  
Pore Pressure Prediction ◽  
Drilling Operations ◽  
Artificial Neural

Pore pressure is a critical parameter in designing drilling operations. Inaccurate pore pressure data can cause problems, even incidents in drilling operations. Pore pressure data can be obtained from direct measurement methods or estimated using indirect measurement methods such as empirical models. In the oil and gas industry, most of the time, direct measurement is only taken in certain depth due to relatively high costs. Hence, empirical models are commonly used to fill in the gap. However, most of the empirical models highly depend on specific basins or types of formation. Furthermore, to predict pore pressure using empirical models accurately requires a good understanding in determining Normal Compaction Trendline. This proposed approach aims to find a more straightforward yet accurate method to predict pore pressure. Using Artificial Neural Network Model as an alternative method for pore pressure prediction based on logging data such as gamma-ray, density, and sonic log, the result shows a promising accuracy.

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

scholarly journals Pre-drill pore pressure prediction and safe well design on the top of Tulamura anticline, Tripura, India: a comparative study

2019 ◽  
Vol 10 (3) ◽  
pp. 1021-1049
Author(s):  
Mohatsim Mahetaji ◽  
Jwngsar Brahma ◽  
Anirbid Sircar
Keyword(s):  
Pore Pressure ◽  
Seismic Data ◽  
New Method ◽  
Burst Pressure ◽  
Velocity Data ◽  
Pressure Data ◽  
Collapse Pressure ◽  
Fracture Pressure ◽  
Well Design ◽  
Pore Pressure Prediction

AbstractThe Tulamura anticline falls in the state Tripura, Northeast India. The anticline is extended up to neighbour country Bangladesh. The region is characterized by huge anticlines, normal faults and abnormally pressured formations which causes a wide margin of uncertainties in wildcat well planning and design. These geological complexities of Tulamura anticline make the drilling engineers more challenging. Therefore, a proper well design is essential in such a region to prevent blowout. Drilling engineer requires to maintain wellbore pressure between the pore pressure and fracture pressure to reduce the possibility of a kick and a formation damage. Pore pressure plays an important role to design a safe and economical well in such a high pressure and temperature reservoir. For wildcat drilling, only seismic data are available in the study area. There are various methods to predict pore pressure from seismic velocity data. Modified Eaton’s method is widely used for the pore pressure prediction from seismic data in terms of the velocity ratio. Modified Eaton’s equations may cause an error by manual selection of compaction trend line which is used to find normal compaction velocity. The main objectives of this study are to develop a new method to predict pore pressure and safe well design on the top of Tulamura anticline in terms of pore pressure. The new method is validated by a well-known method, modified Eaton’s method, and RFT pressure data from offset wells. An excellent match with pore pressures estimated from RFT pressure data and predicted by new model along with modified Eaton’s method is observed in this research work. The efficiency and accuracy level of the hybrid model is more as compared to other methods as it does not require compaction velocity data; thus, an error caused by manual compaction trend can be eliminated. Pore pressure predicted by new method indicates result up to the 6000 m, which is up to the basement rock. The predicted pore pressures by new method are used as an input to calculate the fracture pressure by Hubbert and Willis method, Mathews and Killy method and modified Eaton’s method. Equivalent mud weight selection is carried out using median line principle with additional 0.3 ppg, 0.3 ppg and 0.2 ppg of swab pressure, surge pressure and safety factor, respectively, for calculation of all casing pipes. Casing setting depths are selected based on pore pressure gradient, fracture pressure gradient and mud weight using graphical method. Here, four types of casing setting depths are selected: conductor, surface, intermediate and production casings at 100 ft, 6050 ft, 15500 ft and 18,500 ft, respectively, by new methods, but the casing setting depths for intermediate are at 13500 ft in the case of modified Eaton’s method. The casing policy is selected based on burst pressure, collapse pressure and tension load. For each casing, kick tolerance in bbl is determined from kick tolerance graph to prevent the blowout. Finally, comparative safe and economical wells are designed on the top of Tulamura anticline along with target depth selection, casing setting depth selection, casing policy selection and kick tolerance in consideration of collapse pressure, burst pressure and tension load which gives a clear picture of well planning on the top of anticline in pore pressure point of view.

Electrofacies in gas shale from well log data via cluster analysis: A case study of the Perth Basin, Western Australia

2014 ◽  
Vol 6 (3) ◽  
Author(s):  
Amir Torghabeh ◽  
Reza Rezaee ◽  
Reza Moussavi-Harami ◽  
Biswajeet Pradhan ◽  
Mohammad Kamali ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
Gamma Ray ◽  
Cost Effective ◽  
Gas Production ◽  
Sonic Log ◽  
Cost Effective Method ◽  
Distance Data ◽  
Resistivity Log ◽  
Gamma Ray Log

AbstractIdentifying reservoir electrofacies has an important role in determining hydrocarbon bearing intervals. In this study, electrofacies of the Kockatea Formation in the Perth Basin were determined via cluster analysis. In this method, distance data were initially calculated and then connected spatially by using a linkage function. The dendrogram function was used to extract the cluster tree for formations over the study area. Input logs were sonic log (DT), gamma ray log (GR), resistivity log (IND), and spontaneous potential (SP). A total of 30 reservoir electrofacies were identified within this formation. Integrated geochemical and petrophysics data showed that zones with electrofacies 3, 4, 9, and 10 have potential for shale gas production. In addition, the results showed that cluster analysis is a precise, rapid, and cost-effective method for zoning reservoirs and determining electrofacies in hydrocarbon reservoirs.

Predrill pore‐pressure prediction using seismic data

Geophysics ◽  
2002 ◽  
Vol 67 (4) ◽  
pp. 1286-1292 ◽  
Author(s):  
C. M. Sayers ◽  
G. M. Johnson ◽  
G. Denyer
Keyword(s):  
Velocity Field ◽  
Gulf Of Mexico ◽  
Pore Pressure ◽  
Seismic Data ◽  
Seismic Velocities ◽  
Pressure Data ◽  
Pore Pressure Prediction ◽  
Well Data ◽  
Interval Velocities ◽  
Reflection Tomography

1A predrill estimate of pore pressure can be obtained from seismic velocities using a velocity‐to–pore‐pressure transform, but the seismic velocities need to be derived using methods having sufficient resolution for well planning purposes. For a deepwater Gulf of Mexico example, significant differences are found between the velocity field obtained using reflection tomography and that obtained using a conventional method based on the Dix equation. These lead to significant differences in the predicted pore pressure. Parameters in the velocity‐to–pore‐pressure transform are estimated using seismic interval velocities and pressure data from nearby calibration wells. The uncertainty in the pore pressure prediction is analyzed by examining the spread in the predicted pore pressure obtained using parameter combinations which sample the region of parameter space consistent with the available well data. If calibration wells are not available, the ideas proposed in this paper can be used with measurements made while drilling to predict pore pressure ahead of the bit based on seismic velocities.

scholarly journals Pore Pressure Prediction using Well-Logging Data in the West Baram Delta, Offshore Sarawak Basin, Malaysia

2019 ◽  
Vol 8 (4) ◽  
pp. 9172-9178
Keyword(s):  
Pore Pressure ◽  
Transit Time ◽  
Oil Recovery ◽  
Oil And Gas ◽  
Gamma Ray ◽  
Reservoir Modeling ◽  
Gas Field ◽  
Overburden Pressure ◽  
Trend Line ◽  
Pore Pressure Prediction

Well-predicted pore pressure is vital throughout the lifetime of an oil and gas field starting from exploration to the production stage. Here, we studied a mature field where enhanced oil recovery is of high interest and pore pressure data is crucial. Moreover, the top of the overpressure zone in west Baram Delta starts at different depths. Hence, valid pore pressure prediction prior to drilling is a prerequisite for reducing drilling risks, increasing efficient reservoir modeling and optimizing costs. Petrophysical logs such as gamma-ray, density logs, and sonic transit time were used for pore pressure prediction in the studied field. Density logs were used to predict the overburden pressure, whereas sonic transit time, and gamma-ray logs were utilized to develop observed shale compaction trend line (OSCTL) and to establish a normal compaction trend line (NCTL). Pore pressure was predicted from a locally observed shale compaction trend line of 6 wells using Eaton’s and Miller's methods. The predicted pore pressure using Eaton’s DT method with Eaton’s exponent 3 showed a better matching with the measured pressure acquired from the repeat formation test (RFT). Hence, Eaton’s DT method with Eaton exponent 3 could be applied to predict pore pressure for drilling sites in the study area and vicinity fields with similar geological settings.

scholarly journals Formation Pore Pressure Variation of the Neocomian Sedimentary Succession (the Fahliyan Formation) in the Abadan Plain Basin, SW of Iran

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Bahman Soleimani ◽  
Mohammad Hassani-Giv ◽  
Iraj Abdollahi fard
Keyword(s):  
Pore Pressure ◽  
Middle Part ◽  
Burial Depth ◽  
Pressure Data ◽  
Pressure Step ◽  
Data Points ◽  
Sedimentary Succession ◽  
Pressure Regime ◽  
Formation Pore Pressure

The Neocomian Fahliyan Formation is one of the important oil reservoirs in the Abadan Plain Basin, SW of Iran. To evaluate the pore pressure regime of the Fahliyan reservoir, 164 in situ pressure data points (MDT, XPT, and RFT) were analyzed from seven wells belonging to six oilfields. The pressure versus depth plot revealed that the Fahliyan reservoir is highly overpressured in all fields. The formation was characterized as a multilayered stacked reservoir with different pore pressure decreasing downward in a step-wise manner. Also, there is a major pressure step in the middle part of the reservoir, suggesting the presence of a regional efficient seal dividing the reservoir into two stacked compartments, where the upper compartment is more overpressured than the lower one. The stepped pressure pattern of the Fahliyan Formation is a regional phenomenon controlled by a factor governed regionally, the depositional condition, and facies lateral changes during the deposition of shallowing upward sequence of the Fahliyan reservoir. In addition, direct relationship is observed between the reservoir pressure and burial depth. This matter could amplify the initially generated overpressure state more possible due to dewatering of sediments and by-pass product of oil migration from Garau source rock to the Fahliyan reservoir.

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