Predrill pore-pressure prediction and pore pressure and fluid loss monitoring during drilling: A case study for a deepwater subsalt Gulf of Mexico well and discussion on fracture gradient, fluid losses, and wellbore breathing

2014 ◽  
Vol 2 (1) ◽  
pp. SB45-SB55 ◽  
Author(s):  
Fernando Enrique Ziegler ◽  
John F. Jones
Keyword(s):  
Gulf Of Mexico ◽  
Pore Pressure ◽  
Horizontal Stress ◽  
Fluid Loss ◽  
Pressure Profiles ◽  
Pore Pressure Prediction ◽  
Fracture Gradient ◽  
Minimum Horizontal Stress ◽  
Fluid Losses

In this case study, the overburden, pore-pressure, and fracture gradients are calculated for several nearby analog wells and subsequently used to generate a predrill pore-pressure prediction for the deepwater subsalt Gulf of Mexico well, Flying Dutchman, located in Green Canyon 511 no. 1 (OCS-G 22971). Two key analog wells penetrated the lower Miocene and have sufficient data to generate pore-pressure profiles. Subsequently, the predrill pore-pressure prediction is found to be in good agreement with the pore pressure estimated from well logs while drilling. During the drilling phase of the Flying Dutchman well, two zones of significant fluid loss and wellbore breathing were encountered and are evaluated as a means of determining the formation types where they are most likely to occur, as well as their related minimum horizontal stress and fracture gradient.

Triple MPD Technique for Drilling and Intelligent Completion Deployment on an Abandoned Deepwater Well

2021 ◽  
Author(s):  
André Alonso Fernandes ◽  
Eduardo Schnitzler ◽  
Fabio Fabri ◽  
Leandro Grabarski ◽  
Marcos Vinicius Barreto Malfitani ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Fluid Loss ◽  
Final Project ◽  
Well Design ◽  
Open Hole ◽  
Loss Control ◽  
Fluid Losses ◽  
Complex Cases ◽  
Total Fluid

Abstract This is a case study of a presalt well that required the use of 3 different MPD techniques to achieve its goals. The well was temporary abandoned when conventional techniques failed to reach the final depth. Total fluid losses in the reservoir section required changing the well design and its completion architecture. The new open hole intelligent completion design had to be used to deliver the selective completion in this challenging scenario. From the hundreds of wells drilled in the Santos basin presalt, there are some wells with tight or no operational drilling window. In order to drill these wells different MPD techniques are used. In most cases, the use of Surface Backpressure (SBP) technique is suitable for drilling the wells to its final depth. For the more complex cases, when higher fluid loss rates occur, the use of SBP and Pressurized Mud Cap Drilling (PMCD) enables the achievement of the drilling and completion objectives. After the temporary abandonment of this specific well in 2018, the uncertainty of the pore pressure could not ensure that the SBP and PMCD techniques would be applicable when reentering the well. To avoid difficult loss control operations, the completion team changed the intelligent completion design to include a separated lower completion, enabling its installation with the MPD system. Besides the previously used MPD techniques, the integrated final project considered an additional technique, Floating Mud Cap Drilling (FMCD), as one of the possible contingencies for the drilling and completion phases. Well reentry and drilling of the remaining reservoir section included the use all the previously mentioned MPD techniques (SBP, PMCD and FMCD). The lower completion deployment utilized the FMCD technique to isolate the formation quickly and efficiently, without damaging the reservoir. The planning and execution of the well faced additional difficulties due to the worldwide pandemic and personnel restrictions. The success from the operation was complete with no safety related events and within the planned budget. At the end, the execution team delivered a highly productive well with an intelligent completion system fully functional, through an integrated and comprehensive approach. MPD use on deepwater wells is relatively new. Different operators used several approaches and MPD techniques to ensure safety and success during wells constructions over the last decade. This paper demonstrates the evolution of MPD techniques usage on deepwater wells.

Digitized Uncertainty Handling of Pore Pressure and Mud-Weight Window Ahead of Bit: North Sea Example

SPE Journal ◽  
2019 ◽  
Vol 25 (02) ◽  
pp. 529-540
Author(s):  
Ane E. Lothe ◽  
Pierre Cerasi ◽  
Manuel Aghito
Keyword(s):  
Pore Pressure ◽  
North Sea ◽  
Failure Criteria ◽  
Horizontal Stress ◽  
Traffic Light ◽  
Data Set ◽  
Pressure Profiles ◽  
Weight Window ◽  
Frictional Coefficients ◽  
Fracture Gradient

Summary A digitized workflow from predrill pore-pressure modeling with a Monte Carlo approach until update of the pressure prognosis while drilling from (for example) sonic or resistivity data is described. The approach has the potential to reduce the uncertainty in the predicted mud-weight window ahead of the bit. For the 3D pressure modeling, a basin modeling software is used, where the pressure compartments in the study area are defined by faults interpreted from seismic. Pressure generation and dissipation are calculated for the study area over millions of years, as the basin was subsiding and compaction was taking place. Key input parameters such as minimum horizontal stress, vertical stress, and frictional coefficients for failure criteria are varied. The output is pore-pressure profiles along the planned well path, with uncertainties. The work presented in this paper was carried out on a North Sea data set. The results show that the uncertainty in the pore pressures will highly influence the uncertainty span in both the fracture gradient and the collapse gradient. Representing the mud-weight window in terms of the most likely collapse and fracturing curve, with corresponding minimum and maximum pore-pressure-derived limits on each side, makes for a more realistic prediction. It presents the uncertainty in the result in a simple visual form, using a “traffic light” approach. While drilling, log data will automatically be used to update the pressure and mud-weight prognosis ahead of bit. The digital updated prognosis can help the drilling crew in decision making during drilling campaigns.

A MODIFIED FRACTURE GRADIENT RELATION AND ITS APPLICATION TO EAST TEXAS AND THE TIMOR SEA

1997 ◽  
Vol 37 (1) ◽  
pp. 536
Author(s):  
R.R. Hillis ◽  
D.G. Crosby ◽  
A.K. Khurana
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Poisson’S Ratio ◽  
Horizontal Stress ◽  
Tectonic Stress ◽  
Poisson's Ratio ◽  
East Texas ◽  
Timor Sea ◽  
Fracture Gradient ◽  
Minimum Horizontal Stress

Theoretical fracture gradient relations are generally based on the assumption that the sedimentary sequence behaves elastically under conditions of lateral constraint. Hence the minimum horizontal stress (σhmin) is given by: where V is Poisson's ratio, σv is overburden stress, pp is pore pressure, and at is far -field tectonic stress. In driling practice, fracture initiation, or leak -off pressures, which are related to σhmin are most commonly predicted by the application of empirical stress /depth relations such as that proposed for offshore Western Australia by Vuckovic (1989): Leak -off pressure (psi) = 0.197D1145, where D is depth in feet. A modified form of the uniaxial elastic relation for the prediction of σhmin is proposed, such that: where the constants c and d are straight line regression constants derived from cross -plotting effective minimum horizontal stress and effective vertical stress. This relation, as opposed to previous empirical approaches to fracture gradient /σhmin determination, yields regression coefficients of physical significance: c represents the average Poisson's ratio term, v /(1 -v), and d represents an estimate of the tectonic (and inelastic) component of the minimum horizontal stress. This application of the modified fracture gradient relation, termed the effective stress cross -plot method, is tested successfully against published data from experimental wells in the East Texas Basin where independent estimates of Poisson's ratio are available. Leak -off pressures have been compiled from 61 wells in the Timor Sea. Leak -off pressures in the Timor Sea are somewhat lower than predicted by Vuckovic's (1989) stress /depth relation for offshore Western Australia, and a new, empirical stress /depth relation, which better fits the Timor Sea data is proposed: The effective stress cross -plot method is also applied to the Timor Sea data, yielding: Detailed pore pressure data were not available for the Timor Sea data -set and the effective stress cross -plot method does not fit the observed data any better than the new empirical stress /depth relation. However, the regression constants suggest an average Poisson's ratio of 0.26 and a relatively insignificant tectonic stress of 1 MPa for the Timor Sea.

Ahead of Bit Pore Pressure Prediction using VSP - A Case Study in South China Sea

2010 ◽  
Author(s):  
Yuhong Xie ◽  
Jun Cai ◽  
Ling Xia Zhen ◽  
Hong Tian ◽  
Yan Hua Li ◽  
...  
Keyword(s):  
South China Sea ◽  
Pore Pressure ◽  
South China ◽  
China Sea ◽  
Pore Pressure Prediction

scholarly journals Elastic characteristics of overpressure due to smectite-to-illite transition based on micromechanism analysis

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. WA23-WA42
Author(s):  
Xuan Qin ◽  
De-Hua Han ◽  
Luanxiao Zhao
Keyword(s):  
Pore Pressure ◽  
Rock Physics ◽  
Fluid Loss ◽  
Sonic Velocity ◽  
Modeling Framework ◽  
Evolution Characteristics ◽  
Rock Physics Modeling ◽  
Pore Pressure Prediction ◽  
Bulk Volume ◽  
Physics Modeling

Characterizing the elastic signatures of overpressure of shale caused by the smectite-to-illite transition relies on a good understanding of this mechanism and is also necessary for pore-pressure prediction. Methods of pore-pressure prediction in shales that have undergone smectite-to-illite transition are mostly based on empirical fitting without a quantitative interpretation based on a micromechanism analysis. With upscaled wireline-logging data, two trends of smectite-to-illite transition are categorized by using the crossplot of sonic traveltime and density. Trend I associated with a fluid-expansion scenario exhibits a decrease of sonic velocity with little change in the bulk density, whereas trend II induced by a fluid-loss scenario contains an increase of density with little change in the sonic velocity. The fluid expansion typically gives rise to high-magnitude overpressure and tends to happen when the overlying formations have more shaly contents and low permeability. The fluid loss case tends to have relatively deeper overpressure onsets, and its overlying formations tend to have more sandy contents with relatively high permeability. We develop a modeling framework to capture the elastic and pore-pressure evolution characteristics in shale during the smectite-to-illite transition. With proper bulk volume models, the velocity, density, and pore pressure increase of shale can be computed in the fluid expansion, fluid loss, and a mixture of these two scenarios. After calibration with logging data, rock-physics modeling can quantitatively interpret the rock-property evolution characteristics within the smectite-to-illite transition zone.

Pore pressure prediction while drilling: Three-dimensional earth model in the Gulf of Mexico

AAPG Bulletin ◽  
2018 ◽  
Vol 102 (04) ◽  
pp. 691-708 ◽  
Author(s):  
Fausto Mosca ◽  
Thomas Hantschel ◽  
Obren Djordjevic ◽  
Jim McCarthy ◽  
Ana Krueger ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Pore Pressure ◽  
Three Dimensional ◽  
Earth Model ◽  
Pore Pressure Prediction

Seismic pore pressure prediction without well data and poorly defined normal compaction trend lines: a case study from the Río Bravo Delta, Northern Mexico

2005 ◽  
Author(s):  
Juan C. Clarembaux ◽  
Marcelo Giusso ◽  
Roberto Gullco ◽  
Daniel Mujica ◽  
Carlos Carabeo Miranda ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Northern Mexico ◽  
Pore Pressure Prediction ◽  
Rio Bravo ◽  
Well Data
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