Modeling Pore Pressure, Fracture Pressure and Collapse Pressure Gradients in Offshore Panna, Western India: Implications for Drilling and Wellbore Stability

2020 ◽  
Vol 29 (4) ◽  
pp. 2717-2734 ◽  
Author(s):  
Souvik Sen ◽  
Ashani Kundan ◽  
Mithilesh Kumar
Keyword(s):  
Pore Pressure ◽  
Wellbore Stability ◽  
Western India ◽  
Pressure Gradients ◽  
Collapse Pressure ◽  
Fracture Pressure

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.

Reclaiming the Operating Window: A Managed Pressure Cementing Workflow to Achieve Zonal Isolation Success in a Mature Field

2021 ◽  
Author(s):  
Jeffrey Smith ◽  
Lucas Rossi ◽  
Christopher Mehler ◽  
Jon Todd Eberhardt ◽  
Christopher Scarborough ◽  
...  
Keyword(s):  
Best Practices ◽  
Pore Pressure ◽  
Stability Control ◽  
Wellbore Stability ◽  
Optimized Design ◽  
Additional Time ◽  
Fracture Pressure ◽  
Increased Risk ◽  
Zonal Isolation ◽  
Operating Window

Abstract Successfully cementing production casing strings is one of the main challenges of well construction in mature fields. The implementation of cementing best practices can be difficult in the narrow pore pressure-fracture pressure (PPFG) window associated with reservoir depletion and complex well architecture. The increased risk of losses can lead operating teams to compromise on these best practices, often jeopardizing the zonal isolation objectives. This can result in significant additional time, cost, and production deferral/loss. Managed pressure cementing (MPC) is a viable technique to address these challenges. Using the managed pressure drilling (MPD) system's capability to precisely control bottomhole pressure, coupled with the use of mud weights that are lower than conventionally needed can expand the PPFG window; enabling operating teams to achieve a higher success rate in meeting the zonal isolation objectives. This paper will offer an optimized design methodology and critical considerations and parameters for MPC operations. It will also briefly describe the primary applications of MPC and specific, unique design considerations associated with each, namely, (1) mud weight less than pore pressure (PP), (2) losses prevention, and (3) wellbore stability control. Lastly, it will provide a case history illustrating how MPC was used in one of the operator's mature fields, by giving an overview of the job engineering design process, the operational planning (inclusive of contingencies), and the key highlights and learnings observed during execution.

Wellbore Stability of Salt and Anhydrite Formation of Fauqi Oilfield in Iraq

2014 ◽  
Vol 641-642 ◽  
pp. 462-468
Author(s):  
Yun Long Mu ◽  
Lei Wang ◽  
Ke Ming Liu ◽  
Jin Gen Deng ◽  
Bao Hua Yu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Wellbore Stability ◽  
Drilling Process ◽  
Power Law Model ◽  
Lower Strength ◽  
Creep Properties ◽  
Collapse Pressure ◽  
Wellbore Instability ◽  
Fracture Pressure ◽  
Salt Creep

Salt and anhydrite formation of Fauqi oilfield in Iraq contains salt, anhydrite and shale. Complex situations have occurred in drilling process, such as overflow and sticking. The cores of the three lithology rock are fetched and their strength and creep mechanical properties are tested. Anhydrite is with higher strength and lower creep properties, and shale and salt is with lower strength and higher creep properties. The collapse pressure and fracture pressure of the three lithology rock are calculated. The safe density window of anhydrite is the most widest and there is no risk of wellbore instability, and the safe density window of shale is the narrowest and wellbore instability easily occur. The low limit of mud density to prevent shale and salt creep are calculated by power law model. The safe drilling density window is determined and successfully applied in drilling field.

A Comprehensive Wellbore Stability Model Considering Poroelastic and Thermal Effects for Inclined Wellbores in Deepwater Drilling

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Xuyue Chen ◽  
Deli Gao ◽  
Jin Yang ◽  
Ming Luo ◽  
Yongcun Feng ◽  
...  
Keyword(s):  
Thermal Effects ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Wellbore Stability ◽  
Pressure Gradients ◽  
Stress Regime ◽  
Collapse Pressure ◽  
Wellbore Instability ◽  
Deepwater Drilling ◽  
Stability Model

Exploring and developing oil and gas in deepwater field is an important trend of the oil and gas industry. Development of deepwater oil and gas fields from a platform always requires a number of directional wells or extended reach wells targeting to different depth of water in various azimuth. Drilling of these wells is mostly associated with a series of wellbore instability problems that are not encountered in onshore or shallow water drilling. In the past decades, a number of studies on wellbore stability have been conducted. However, few of the models are specific for wellbore stability of the inclined deepwater wellbores. In this work, a comprehensive wellbore stability model considering poroelastic and thermal effects for inclined wellbores in deepwater drilling is developed. The numerical method of the model is also presented. The study shows that for a strike-slip stress regime, the wellbore with a low inclination poses more risk of wellbore instability than the wellbore with a high inclination. It also shows that cooling the wellbore will stabilize the wellbore while excessive cooling could cause wellbore fracturing, and the poroelastic effect could narrow the safe mud weight window. The highest wellbore collapse pressure gradients at all of the analyzed directions are obtained when poroelastic effect is taken into account meanwhile the lowest wellbore fracture pressure gradients at all of the analyzed directions are obtained when both of poroelastic effect and thermal effect are taken into account. For safe drilling in deepwater, both of thermal and poroelastic effects are preferably considered to estimate wellbore stability. The model provides a practical tool to predict the stability of inclined wellbores in deepwater drilling.

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.

Study on Borehole Stability of Unconsolidated Sandstone in Depleted Reservior

2012 ◽  
Vol 616-618 ◽  
pp. 720-725
Author(s):  
Qiang Tan ◽  
Jin Gen Deng ◽  
Bao Hua Yu
Keyword(s):  
Oil And Gas ◽  
Drilling Fluid ◽  
Wellbore Stability ◽  
Formation Pressure ◽  
Borehole Stability ◽  
Oil And Gas Development ◽  
Collapse Pressure ◽  
Lost Circulation ◽  
Fracture Pressure ◽  
Pressure Depletion

Reservoir pressure will decline generally along with production in the oil and gas development process. There are some problems such as borehole collapse or reduced diameter and lost circulation in drilling of initial production stage in unconsolidated sandstone. As the formation pressure declines the stress around borehole changes, and then collapse pressure and fracture pressure are affected. Especially in directional wells, variation of wellbore stability is more complex with different borehole deviation and azimuth. The calculation models of collapse and fracture pressure in depleted reservoirs were established, and relevant data in unconsolidated sand reservoir of an oilfield in Bohai Sea was used to calculate collapse pressure and fracture pressure of directional wells in the condition of pressure depletion before and after. The results showed that collapse and fracture pressure decreased as formation pressure depletion, and safe drilling fluid density window was wider when drilled to the direction of minimum horizontal principle stress. The calculation results can be reference to drilling design of adjustment wells in unconsolidated sandstones.

Numerical Investigation of the Influence of the Drill String Vibration Cyclic Loads on the Time Dependent Wellbore Stability Analysis

2021 ◽  
Author(s):  
Arnaud Regis Kamgue Lenwoue ◽  
Jingen Deng ◽  
Yongcun Feng ◽  
Naomie Beolle Songwe Selabi
Keyword(s):  
Cyclic Load ◽  
Drill String ◽  
Wellbore Stability ◽  
Time Dependent ◽  
Cyclic Loads ◽  
Drilling Mud ◽  
Collapse Pressure ◽  
Wellbore Instability ◽  
String Vibration ◽  
Fracture Pressure

Abstract Wellbore instability is one of the most important causes of Non-Productive Time causing billions of dollars of losses every year in the petroleum industry. During the drilling operations, the drilling mud is generally utilized to maintain the wellbore stability. However, the drilling mud is subjected to fluctuations caused by several processes such as the drill string vibration cyclic loads which can result into wellbore instability. In this paper, a nonlinear finite element software ABAQUS is utilized as the numerical simulator to evaluate the time dependent pore pressure and stress distribution around the wellbore after integration of drill string vibration cyclic loads. A MATLAB program is then developed to investigate the wellbore stability by computation of the time dependent wellbore collapse pressure and fracture pressure. The numerical results showed that the safe mud window which was initially constant became narrower with the time after integration of vibration cyclic load. The collapse pressure without vibration cyclic load increased by 14.33 % at the final simulation time while the fracture pressure decreased by 13.80 %. Interestingly, the safe mud windows widened with the increase of the normalized wellbore radius as the wellbore fracture pressure increased and the collapse pressure decreased. This study provides an insight into the coupling of the wellbore stability and the continuous cyclic loads generated by drill string vibrations which is an aspect that has been rarely discussed in the literature.

Research on Wellbore Stability in Formation with Anisotropic Strength

2013 ◽  
Vol 765-767 ◽  
pp. 3151-3157
Author(s):  
Hui Zhang ◽  
Fang Jun Ou ◽  
Guo Qing Yin ◽  
Jing Bing Yi ◽  
Fang Yuan ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Drilling Fluid ◽  
Wellbore Stability ◽  
Rock Body ◽  
Collapse Pressure ◽  
Wellbore Instability ◽  
Transversely Isotropic Rock ◽  
Fracture Development ◽  
Anisotropic Formation ◽  
The Impact

As most of sedimentary rocks are anisotropic, it is significant to research the impact of the anisotropy of strength on wellbore stability in drilling engineering. Particularly, in the Kuqa piedmont exploration area, the anisotropy of strength caused by various jointed surfaces, fracture surfaces and fault planes in formation cause the formation of several groups of weak low-intensity planes traversing borehole . These weak planes will become failure earlier than the rock body in the context of strong stress and high pore pressure, causing chipping, breakouts and sticking. If fractures have good permeability and drilling fluid column pressure is greater than pore pressure, loss may occur. The loss pressure would not be controlled by fracturing pressure and horizontal minimum principal stress, but it depends on the relationship between fracture occurrence and triaxial stress state. In the event of loss, the drilling fluid will flow into these weak structural planes, causing the decrease of friction between rocks and increase of wellbore instability. As a result, for strongly anisotropic formation, the collapse pressure and leakage pressure of weak planes are key factors for evaluating well drilling stability. In this study, according to the stability evaluation on the transversely isotropic rock mechanics in Keshen zone of Kuqa piedmont, the impacts of fracture development on wellbore instability is analyzed; relevant suggestions on engineering geology for the special pressure window in strong anisotropic formation are also put forward.

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