Wellbore Strengthening Design Criteria and Enhanced Fracture Gradient for Widening Stable Mud Weight Window and Enabling Safe and Efficient Drilling in Depleted Reservoirs

2021 ◽  
Author(s):  
Chee Phuat Tan ◽  
Wan Nur Safawati Wan Mohd Zainudin ◽  
M Solehuddin Razak ◽  
Siti Shahara Zakaria ◽  
Thanavathy Patma Nesan ◽  
...  
Keyword(s):  
Particle Size ◽  
Ct Scan ◽  
Design Criteria ◽  
Drilling Mud ◽  
Fracture Width ◽  
Wellbore Strengthening ◽  
Fracture Gradient ◽  
Mud Loss ◽  
Gradient Enhancement ◽  
Compound Particle

Abstract Drilling in permeable formations, especially depleted reservoirs, can particularly benefit from simultaneous wellbore shielding and strengthening functionalities of drilling mud compounds. The ability to generate simultaneous wellbore shielding and strengthening in reservoirs has potential to widen stable mud weight windows to drill such reservoirs without the need to switch from wellbore strengthening compound to wellbore shielding compound, and vice-versa. Wellbore shielding and strengthening experiments were conducted on three outcrop sandstones with three mud compounds. The wellbore shielding stage was conducted by increasing the confining and borehole pressures in 4-5 steps until both reached target pressures. CT scan images demonstrate consistency of the filtration rates with observed CT scanned mud cakes which are dependent on the sandstone pore size and mud compound particle size distributions. In wellbore strengthening stage, the borehole pressure was increased until fracture was initiated, which was detected via borehole pressure trend and CT scan imaging. The fractures generated were observed to be plugged by mud filter solids which are visible in the CT scan images. The extent of observed fracture solid plugging varies with rock elastic properties, fracture width and mud compound particle size distribution. Based on the laboratory test data, fracture gradient enhancement concept was developed for the mud compounds. In addition, the data obtained and observations from the tests were used to develop optimal empirical design criteria and guidelines to achieve dual wellbore strengthening and shielding performance of the mud compounds. The design criteria were validated on a well which was treated with one of the mud compounds based on its mud loss events during drilling and running casing.

Enhancement of Plastering Effect on Strengthening Wellbore by Optimizing Particle Size Distribution of Wellbore Strengthening Materials

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Wenhao He ◽  
Asadollah Hayatdavoudi ◽  
Keyong Chen ◽  
Kaustubh Sawant ◽  
Qin Zhang ◽  
...  
Keyword(s):  
Particle Size ◽  
Tensile Strength ◽  
Particle Size Distribution ◽  
Wellbore Stability ◽  
Strengthening Effect ◽  
Rock Matrix ◽  
Pore Throat ◽  
The Mean ◽  
Wellbore Strengthening ◽  
Mud Loss

Wellbore strengthening materials (WSMs) have been widely used to strengthen the wellbore stability and integrity, especially those lost circulation materials (LCMs) used for mud loss impairment. To enhance the wellbore strengthening effect rather than a loss impairment, plastering effect can be used to increase the fracture gradient of the wall and minimize the probability of inducing new fractures. This is done by smearing the mudcake and pores and forming an internal cake inside the rock matrix using WSMs (or LCMs). Until now, the particle size distribution (PSD) of LCMs have been widely studied for the minimization on the mud loss (e.g., Abran’s rule, ideal packing theory, D90 rule, Halliburton D50 rule, etc.). However, there are few empirical rules focused on the maximum wellbore strengthening effect. This study attempts to find the desired PSD of plastering materials to enhance wellbore stability. In this research, the Brazilian test was used to quantify tensile strength. Meanwhile, the filtration characteristics of WSMs through the rock matrix were observed using a scanning electron microscope (SEM) and an energy-dispersive system (EDS). Finally, this paper adopts D50 of WSMs to be the mean pore throat size for a maximum improvement on the rock tensile strength. We have observed that the closer the D50 of WSMs in the WSMs to the mean pore throat size, the stronger the saturated rock matrix.

Wellbore Strengthening in Narrow Margin Drilling

2016 ◽  
Author(s):  
Ogochukwu Benyeogor ◽  
Sunday Awe ◽  
Obinna Amah ◽  
Oseme Ugochukwu ◽  
Adeyemi Erinle ◽  
...  
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Pore Pressure ◽  
Niger Delta ◽  
Wellbore Integrity ◽  
Power Stations ◽  
Energy Demands ◽  
Wellbore Strengthening ◽  
Fracture Gradient ◽  
Mud Loss

ABSTRACT Natural gas is one of the cleanest energy sources, its uses range from fueling power stations to cooking and heating. Global demand for natural gas is expected to rise in the coming years. Meeting these energy demands means drilling deeper exploration and development wells to access huge volumes of gas present under high pressure and high temperature (HPHT) conditions. Despite the attractiveness of the reward, managing the narrow drilling window between the reservoir pore pressure and the formation fracture gradient has remained a major source of cost escalation and non-productive time on HPHT projects. In order to improve the economics of HPHT projects, technologies like Managed Pressure Drilling and borehole strengthening have been used as a means of mitigating the risks associated with narrow margin drilling, thus enabling a paradigm shift from traditional casing seat selection methodology. In the Niger Delta, it is not uncommon to observe significant jumps in pore pressure values in proximate high pressure formations. The simplification of well designs and successful drilling operations are often challenged by the need to navigate through series of high pressured reservoirs in narrow margin windows. Compliance with process safety requirements requires selection of mud weight that is low enough to prevent mud loss and high enough to overbalance the reservoir pressure. Mud loss induced by formation fracture is often encountered in tight margin drilling, and when this happens, the focus shifts to strengthening the damaged wellbore using various techniques such as pumping chemical resins to seal off the loss zones. Various degrees of results have been achieved when borehole strengthening techniques are deployed with the objective of restoring wellbore integrity in both permeable and non-permeable formations. Successful deployments have resulted in achieving the well objectives safely and cost effectively. This paper details loss of wellbore integrity experienced on an HPHT well in the Niger delta and the wellbore strengthening strategy that was used to restore the strength in a non-permeable formation. It sheds light on how understanding the nature of the fracture, rock lithology as well as proper job execution can restore a damaged wellbore to its previous strengths. A Cost reduction approach to the execution of the strategy is also discussed.

A Holistic Approach to Characterize Mud Loss Using Dynamic Mud Filtration Data

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Chinedum Peter Ezeakacha ◽  
Saeed Salehi
Keyword(s):  
Regression Analysis ◽  
Field Application ◽  
Operating Conditions ◽  
Mitigation Strategies ◽  
Drilling Mud ◽  
Experimental Conditions ◽  
Lost Circulation ◽  
Rotary Speed ◽  
Mud Filtration ◽  
Mud Loss

Drilling mud loss in highly porous media and fractured formations has been one of the industry's focuses in the past decades. Wellbore dynamics and lithology complexities continue to push for more research into accurate quantification and mitigation strategies for lost circulation and mud filtration. Conventional methods of characterizing mud loss with filtration data for field application can be time-consuming, particularly because of the interaction between several factors that impact mud loss and filtration. This paper presents a holistic engineering approach for characterizing lost circulation using pore-scale dynamic water-based mud (WBM) filtration data. The approaches used in this study include: factorial design of experiment (DoE), hypothesis testing, analysis of variance (ANOVA), and multiple regression analysis. The results show that an increase in temperature and rotary speed can increase dynamic mud filtration significantly. An increase in lost circulation material (LCM) concentration showed a significant decrease dynamic mud filtration. A combination of LCM concentration and rotary speed showed a significant decrease in dynamic mud filtration, while a combination of LCM concentration and temperature revealed a significant increase in dynamic mud filtration. Rotary speed and temperature combination showed an increase in dynamic mud filtration. The combined effect of these three factors was not significant in increasing or decreasing dynamic mud filtration. For the experimental conditions in this study, the regression analysis for one of the rocks showed that dynamic mud filtration can be predicted from changes in LCM concentration and rotary speed. The results and approach from this study can provide reliable information for drilling fluids design and selecting operating conditions for field application.

Optimum particle size distribution design for lost circulation control and wellbore strengthening

2016 ◽  
Vol 35 ◽  
pp. 836-850 ◽  
Author(s):  
Omid Razavi ◽  
Ali Karimi Vajargah ◽  
Eric van Oort ◽  
Munir Aldin ◽  
Sudarshan Govindarajan
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Circulation Control ◽  
Lost Circulation ◽  
Wellbore Strengthening

An Experimental Investigation of Filtercake Reinforced Wellbore Strengthening and Fracture Sealing

2019 ◽  
Author(s):  
Mingzheng Yang ◽  
Yuanhang Chen ◽  
Frederick B. Growcock ◽  
Feifei Zhang
Keyword(s):  
Experimental Investigation ◽  
Critical Role ◽  
Fracture Initiation ◽  
Fluid Loss ◽  
Lost Circulation ◽  
Fracture Sealing ◽  
Sealing Pressure ◽  
Wellbore Strengthening ◽  
Mud Loss ◽  
Lost Circulation Materials

Abstract Drilling-induced lost circulation should be managed before and during fracture initiation rather than after they propagate to form large fractures and losses become uncontrollable. Recent studies indicated the potentially critical role of filtercake in strengthening the wellbore through formation of a pressure-isolating barrier, as well as plugging microfractures during fracture initiation. In this study, an experimental investigation was conducted to understand the role played by filtercake in the presence of lost circulation materials (LCMs). A modified permeability plugging apparatus (PPA) with slotted discs was used to simulate whole mud loss through fractures of known width behind filtercake. Cumulative fluid loss upon achieving a complete seal and the maximum sealing pressure were measured to evaluate the combined effects of filtercake and LCMs in preventing and reducing fluid losses. The effects of some filtercake properties (along with LCM type, concentration and particle size distribution) on filtercake rupture and fracture sealing were investigated. The results indicate that filtercake can accelerate fracture sealing and reduce total mud loss. Efficiently depositing filtercake while drilling can reduce the concentration of LCM that is required to plug and isolate incipient fractures.

scholarly journals Gradual Meso-Structural Response Behaviour of Characteristics of Asphalt Mixture Main Skeleton Subjected to Load

2019 ◽  
Vol 9 (12) ◽  
pp. 2425 ◽  
Author(s):  
Liwan Shi ◽  
Zhen Yang ◽  
Duanyi Wang ◽  
Xiao Qin ◽  
Xin Xiao ◽  
...  
Keyword(s):  
Particle Size ◽  
Asphalt Mixture ◽  
Structural Response ◽  
Load Resistance ◽  
Development Trend ◽  
Design Criteria ◽  
Coarse Aggregates ◽  
Response Behaviour ◽  
Contact Points ◽  
C Value

In order to provide a reference for the gradation design of dense skeleton asphalt mixtures (DSAM), this study conducts a thorough analysis of the gradual meso-structural response behaviour of characteristics of the asphalt mixture main skeleton subjected to load using the digital image processing (DIP) technique. Moreover, gradation optimisation measures and the design criteria of mesoscopic evaluation indices for the main skeleton are proposed. The results indicate that aggregates with particle sizes of 2.36–4.75 mm can effectively increase the number of contact points; however, the stability of the main skeleton remains insufficient. Furthermore, coarse aggregates with a particle size larger than 4.75 mm provide the most significant contribution to the formation of a steady main skeleton; this is the critical particle size for the formation of a steadier main skeleton. Gradation is the major determinant of mesoscopic evaluation indices, including average coordination number ( n ¯ c ) and the ratio of the quantity of coarse aggregates without contact points to the total quantity of coarse aggregates (C value) for the asphalt mixture of the main skeleton. On the other hand, the performance of asphalt has an insignificant influence on mesoscopic evaluation indices; it mainly affects the development trend of macroscopic rutting. In the design process of DSAM, it is necessary to optimise gradation with the aim of increasing n ¯ c and reducing the C value so as to enhance the load resistance capacity of the primary skeleton. When preparing asphalt mixture specimens using the wheel rolling method, the design criteria for the aforementioned indices are n ¯ c ≥ 1.5 and C ≤ 15%, which can be used as bases for the design of DSAM with a nominal maximum particle size of 13.2 mm to ensure that the coarse aggregates are interlocked and form a steady main skeleton.

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