scholarly journals Geomechanical Analysis for Deep Shale Gas Exploration Wells in the NDNR Blocks, Sichuan Basin, Southwest China

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1117 ◽  
Author(s):  
Majia Zheng ◽  
Hongming Tang ◽  
Hu Li ◽  
Jian Zheng ◽  
Cui Jing
Keyword(s):  
Pore Pressure ◽  
Shale Gas ◽  
Sichuan Basin ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Geomechanical Model ◽  
Stress Regime ◽  
Xujiahe Formation ◽  
Geomechanical Analysis

The abundant reserve of shale gas in Sichuan Basin has become a significant natural gas component in China. To achieve efficient development of shale gas, it is necessary to analyze the stress state, pore pressure, and reservoir mechanical properties such that an accurate geomechanical model can be established. In this paper, Six wells of Neijiang-Dazu and North Rongchang (NDNR) Block were thoroughly investigated to establish the geomechanical model for the study area. The well log analysis was performed to derive the in-situ stresses and pore pressure while the stress polygon was applied to constrain the value of the maximum horizontal principal stress. Image and caliper data, mini-frac test and laboratory rock mechanics test results were used to calibrate the geomechanical model. The model was further validated by comparing the model prediction against the actual wellbore failure observed in the field. It was found that it is associated with the strike-slip (SS) stress regime; the orientation of SHmax was inferred to be 106–130° N. The pore pressure appears to be approximately hydrostatic from the surface to 1000 m true vertical depth (TVD), but then becomes over-pressured from the Xujiahe formation. The geomechanical model can provide guidance for the subsequent drilling and completion in this area and be used to effectively avoid complex drilling events such as collapse, kick, and lost circulation (mud losses) along the entire well. Also, the in-situ stress and pore pressure database can be used to analyze wellbore stability issues as well as help design hydraulic fracturing operations.

APPLICATION OF GUIDELINE CHARTS IN DECISIONMAKING ON WELL TRAJECTORY AND MUD WEIGHT PROGRAM

2001 ◽  
Vol 41 (1) ◽  
pp. 609
Author(s):  
X. Chen ◽  
C.P. Tan ◽  
C.M. Haberfield
Keyword(s):  
Stability Analysis ◽  
Case Studies ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Material Strength ◽  
Stress Regime ◽  
Wellbore Instability ◽  
Well Trajectory

To prevent or minimise wellbore instability problems, it is critical to determine the optimum wellbore profile and to design an appropriate mud weight program based on wellbore stability analysis. It is a complex and iterative decisionmaking procedure since various factors, such as in-situ stress regime, material strength and poroelastic properties, strength and poroelastic anisotropies, initial and induced pore pressures, must be considered in the assessment and determination.This paper describes the methodology and procedure for determination of optimum wellbore profile and mud weight program based on rock mechanics consideration. The methodology is presented in the form of guideline charts and the procedure of applying the methodology is described. The application of the methodology and procedure is demonstrated through two field case studies with different in-situ stress regimes in Australia and Indonesia.

DYNAMIC FAULT/FRACTURE SEAL BEHAVIOUR AND GEOMECHANICAL ANALYSIS OF THE GREATER GOBE AREA, SOUTHERN HIGHLANDS PROVINCE, PAPUA NEW GUINEA

2001 ◽  
Vol 41 (1) ◽  
pp. 251
Author(s):  
M.C. Daniels ◽  
D.T. Moffat ◽  
D.A. Castillo
Keyword(s):  
Papua New Guinea ◽  
Shear Failure ◽  
New Guinea ◽  
In Situ Stress ◽  
Stress Regime ◽  
Well Spacing ◽  
Geomechanical Analysis ◽  
Near Shore ◽  
Performance Results

The Gobe Main and SE Gobe Fields were discovered in the early 1990s in the Papuan Fold Belt in the Highlands of Papua New Guinea. Heavily karstified Darai Limestone at the surface and heli-supported drilling made field appraisal problematic and expensive. With initial well spacing upwards of several kilometres, these fields were thought to be ‘tank’ type models, with field-wide extrapolations of gas-oil and oil-water contacts.The main Iagifu Sandstone reservoir in the Gobe fields comprises several fluvial and near-shore sand bodies, which are readily correlatable across the fields. The reservoir units display discrete coarsening upward sequences containing medium (~17%) porosity, medium to high permeability (>100 mD) sandstones. Although several different depositional facies are interpreted within the Iagifu reservoir, sand units are extensive on the scale of the Gobe structures and do not appear to be producing significant lateral boundaries or reservoir compartmentalisation.Geomechanical analysis has enabled the calculation of in-situ stress magnitudes and establishment of a geomechanical model for Gobe. Locally, the Gobe Main Field appears to be in a strike-slip stress regime (SHmax>Sv>Shmin). SHmax directions vary from NNE– SSW to NE–SW. Stress magnitudes indicate the structure is near frictional equilibrium, with a high proportion of natural fractures and faults critically stressed for shear failure. Since first oil in early 1998, performance results have indicted pressure segregation of many of the wells in both the Gobe Main and SE Gobe fields. Although only one fault has been positively identified at the reservoir level, the mapped faults appear to have sand-on-sand juxtaposition with minimal (

Transient Coupling of Swab/Surge Pressure and In-Situ Stress for Wellbore-Stability Evaluation During Tripping

SPE Journal ◽  
2018 ◽  
Vol 23 (04) ◽  
pp. 1019-1038 ◽  
Author(s):  
Feifei Zhang ◽  
Yongfeng Kang ◽  
Zhaoyang Wang ◽  
Stefan Miska ◽  
Mengjiao Yu ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Pore Pressure ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Pressure Oscillations ◽  
Deepwater Drilling ◽  
Wellbore Pressure ◽  
Operating Window ◽  
Safe Operating

Summary This paper identifies wellbore-stability concerns caused by transient swab/surge pressures during deepwater-drilling tripping and reaming operations. Wellbore-stability analysis that couples transient swab/surge wellbore-pressure oscillations and in-situ-stress field oscillations in the near-wellbore (NWB) zone in deepwater drilling is presented. A transient swab/surge model is developed by considering drillstring components, wellbore structure, formation elasticity, pipe elasticity, fluid compressibility, fluid rheology, and the flow between wellbore and formation. Real-time pressure oscillations during tripping/reaming are obtained. On the basis of geomechanical principles, in-situ stress around the wellbore is calculated by coupling transient wellbore pressure with swab/surge pressure, pore pressure, and original formation-stress status to perform wellbore-stability analysis. By applying the breakout failure and wellbore-fracture failure in the analysis, a work flow is proposed to obtain the safe-operating window for tripping and reaming processes. On the basis of this study, it is determined that the safe drilling-operation window for wellbore stability consists of more than just fluid density. The oscillation magnitude of transient wellbore pressure can be larger than the frictional pressure loss during the normal-circulation process. With the effect of swab/surge pressure, the safe-operating window can become narrower than expected. The induced pore pressure decreases monotonically as the radial distance increases, and it is limited only to the NWB region and dissipates within one to two hole diameters away from the wellbore. This study provides insight into the integration of wellbore-stability analysis and transient swab/surge-pressure analysis, which is discussed rarely in the literature. It indicates that tripping-induced transient-stress and pore-pressure changes can place important impacts on the effective-stress clouds for the NWB region, which affect the wellbore-stability status significantly.

Numerical Modeling of Sand Production Potential Estimation and Passive Control Optimization: A Case Study

2018 ◽  
Author(s):  
Eva Lopez-Puiggene ◽  
Nubia Aurora Gonzalez-Molano ◽  
Jose Alvarellos-Iglesias ◽  
Jose M. Segura ◽  
M. R. Lakshmikantha
Keyword(s):  
Stress State ◽  
High Resolution ◽  
Plastic Strain ◽  
Pore Pressure ◽  
In Situ Stress ◽  
Point Of View ◽  
Wellbore Stability ◽  
Sand Production ◽  
Production Stress

Solids/sand production is an unintended byproduct of the hydrocarbon production that, from an operational point of view, might potentially lead to undesirable consequences. This paper focuses on a study centered in the geomechanical perspective for solids production. An integrated workflow is presented to analyze the combined effect of reservoir pore-pressure, drawdown, in-situ stress, rock properties and well/perforations orientation on the onset of solid production. This workflow incorporates analyses at multiple scales: rock constitutive modeling at lab scale, 1D geomechanical models at wellbore scale along well trajectories, a 3D geomechanical model at the reservoir scale and 3D/4D high resolution reservoir - geomechanical coupled models at the well and perforation scale. 1D geomechanical models were built using log and field data, drilling experience and laboratory tests in order to characterize in situ stresses, pore pressure and rock mechanics properties (stiffness and strength) profiles for several wells. Rock shear failure mechanism was also analyzed in order to build a pre-drill model and evaluate the wellbore stability from a geomechanical point of view. Pre-production stress modeling was simulated to obtain a representative initial stress state integrating 1D geomechanics well results, 3D dynamic model and seismic interpretations. Mechanical properties were distributed considering properties calculated in the 1D geomechanical models as input. 3D stress field was validated with in-situ stress profiles from 1D modeling results. This simulated pre-production stress state was then used as an initial condition for the reservoir - geomechanical coupled simulations. Effective stress changes and deformations associated to pore pressure changes were calculated including the coupling between reservoir and geomechanical modeling. Finally, a 3D/4D high resolution well scale reservoir - geomechanical coupled numerical model was built in order to determine the threshold of sand production. A limit of plastic strain was obtained based on numerical simulations of available production data, DST and ATWC tests. This critical plastic strain limit was used as a criterion (strain-based) for rock failure to define the onset of sand production as a function of pore pressure, perforation orientation and rock strength. Conclusions regarding the perforation orientations related to the possibility of producing solids can support operational decisions in order to avoid undesirable solid production and therefore optimize the production facilities capacity and design to handle large amounts of solids and/or the clogging of the well.

Near real-time geomechanical modelling update and completion optimisation in the fold belt area of PNG: a case study with Oil Search Ltd

2010 ◽  
Vol 50 (2) ◽  
pp. 725 ◽  
Author(s):  
Katharine Burgdorff ◽  
David Castillo ◽  
Adrian White ◽  
Jon Rowse ◽  
Gavin Douglas ◽  
...  
Keyword(s):  
Real Time ◽  
Pore Pressure ◽  
Image Data ◽  
Wellbore Stability ◽  
Fold Belt ◽  
Geomechanical Model ◽  
High Resolution Image ◽  
Geomechanical Analysis ◽  
Stress Orientations

Collecting high-resolution image data in the majority of currently-drilled wells in the Papuan Fold Belt area has substantially improved our knowledge of the subsurface. A major contribution comes from the observation that the contemporary stress field and the pore pressure environment in the fold belt area are non-uniform. Comprehensive analysis of high-quality LWD images through the overburden has combated uncertainties brought about by the heterogeneity in the stresses and pore pressure. These data have been especially important when updating or constraining a geomechanical model in near real-time for the purpose of providing wellbore stability and completion recommendations. The geomechanical model unique to a particular part of the structure has been combined with finite-element modelling to help identify the optimal completion strategy for the reservoir sands in a number of wells. Recently, the near real-time geomechanical analysis has been used to quickly identify the optimal perforation direction in the reservoir in order to minimise the risk of solids production during completion.Essential data sources for the modelling include LWD images from the reservoir to confirm stress orientations and LWD density data and petrophysical analysis to accurately determine sand strength (UCS). A quick-look analysis uses the calculated UCS profile and the geomechanical model to identify, and therefore avoid perforating, any weak sections of the reservoir. Doing so hopefully mitigates the risk of solids production. This paper outlines the workflow and displays some results from the Papuan Fold Belt area.

Gas-prospective area optimization for Silurian shale gas of Longmaxi Formation in southern Sichuan Basin, China

2015 ◽  
Vol 3 (2) ◽  
pp. SJ49-SJ59 ◽  
Author(s):  
Jiang Yuqiang ◽  
Zhang Qichen ◽  
Zhang Hu ◽  
Gan Hui ◽  
Luo Mingsheng ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Integrated Approach ◽  
In Situ Stress ◽  
Data Set ◽  
Longmaxi Formation ◽  
Marine Shale ◽  
Shale Reservoirs

We investigated the development of a new criterion to quantify and rank marine shale reservoirs of the Lower Silurian Longmaxi Formation and to identify the most prospective area in the southern Sichuan Basin by examining the correlation of various parameters and forming a regionally consistent set. These reliable parameters in our model included geologic factors (rock properties), engineering factors (rock brittleness, in situ stress, and pressure gradient), and topographic factors (pipeline availability and land accessibility). In addition to the common parameters (thickness, depth, porosity, and gas in place), our system used some critical factors associated with complex tectonic evolution and gas preservation in detail, such as in situ stress, pressure gradient, and topographic conditions. An integrated data set was used for designing the well trajectory, creating large volume-induced fractures networks, and increasing the initial production of shale gas. Our integrated approach was used to classify into three ranking levels of Silurian Longmaxi marine shale reservoirs in the Changning area in the southern Sichuan Basin. The integrated approach incorporated a prediction model of pressure gradient and the distribution of in situ stress. The initial production from horizontal wells resulted in a positive assessment as high-performing affordable wells, and served as validation of the methodology used to rank prospective areas.

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