Analytical Model to Characterize “Smear Effect” Observed While Drilling With Casing1

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Aniket Kumar ◽  
Robello Samuel
Keyword(s):  
Case Studies ◽  
Analytical Models ◽  
Reservoir Properties ◽  
Subsequent Increase ◽  
Lost Circulation ◽  
Effect Mechanism ◽  
Open Hole ◽  
Gradient Based ◽  
Wellbore Strengthening ◽  
Fracture Gradient

The “Smear Effect” observed during a casing-while-drilling operation helps reduce lost circulation, provides wellbore strengthening, and improves the fracture gradient so we can drill more effectively through depleted reservoirs. Several case studies have been reported confirming the formation of a smear zone around the wellbore wall, due to the plastering of cuttings and added lost circulation materials. However, even after successful application in a number of cases, a thorough understanding of the parameters affecting the formation of the smear zone and the subsequent increase in the fracture gradient is not available. This study analyses the theory behind the phenomenon of the smear effect mechanism using case studies and existing literature, and then applies analytical models to estimate the improvement in the fracture gradient based on the drilling parameters and reservoir properties. The formation of the smear zone has been investigated by modeling the mechanism of initiation of micro-fractures around the wellbore wall due to high equivalent circulating densities (ECDs) occurring during casing while drilling. The effect of plugging of these generated micro-fractures by the drilled cuttings and additional lost circulation material added has then been modelled, to estimate the resultant improvement in fracture gradients expected along the wellbore open hole section. In addition, the appropriate particle size distribution required to successfully plug the micro-fractures has also been presented. These analytical models have then been applied to a simulated field case study and the results have been analysed in the context of recorded field observations to simulate the smear effect using the proposed models. The contribution of the casing size and length, formation properties, and operating parameters on the initiation of micro-fractures and the increase in fracture gradient has also been presented to better demonstrate the mechanism of the formation of the smear zone. This analysis is one of the first of its kind of theoretical study to understand the fundamentals of the smear effect mechanism and can be suitably applied to enhance our understanding of the smear effect to use it better to our advantage.

Mitigating Well Construction Challenges of a Caspian Deepwater Exploratory Well: A Cementing Perspective

2021 ◽  
Author(s):  
Irfan Kurawle ◽  
Ansgar Dieker ◽  
Adriana Soltero ◽  
Svetlana Nafikova
Keyword(s):  
Pore Pressure ◽  
Long Term Effects ◽  
Lost Circulation ◽  
Well Integrity ◽  
Pore Pressure Prediction ◽  
Wellbore Strengthening ◽  
Selective Placement ◽  
Fracture Gradient ◽  
Comprehensive Modeling

Abstract BP returned to Caspian deepwater exploratory drilling in 2019. The exploration well was drilled on the Shafag-Asiman structure in water depths greater than 2,000 ft. Well challenges included high shallow water flow (SWF) risk with multiple re-spuds on the nearest offset, lost circulation due to complex wellbore geometry combined with a narrow pore and fracture gradient window, and uncertainty in pore pressure prediction in abnormally pressured formations with a new depositional model. In addition, a well total depth more than 23,000 ft, eight string casing design and bottom-hole pressures greater than 20,000 psi presented a truly modern-day challenge to well integrity. A six-month planning phase for the cementing basis of design concluded by delivering slurry designs capable of combating SWF, qualified by variable-speed rotational gel strength measurement. Engineered lost circulation with selective placement of wellbore strengthening materials in combination with cement and mechanical barriers to provide isolation and integrity for the life of the well. Exhaustive pilot testing to account for changes required a cement design based on pore pressure variation and comprehensive modeling for hydraulics, centralizer placement, and mud displacement. This was complemented by a custom centralizer testing process specifically designed to simulate forces exerted in wells with similar complexity. Long-term effects on cement were evaluated, not only for placement but also for future operations including pressure and temperature cycles during wellbore construction or abandonment.

Impact of Static and Dynamic Wellbore Strengthening on Well Planning in Petroleum Development Oman

2021 ◽  
Author(s):  
Peter in 't Panhuis ◽  
Sandeep Mahajan ◽  
Cindy Prin ◽  
Ahmed Al Ajmi
Keyword(s):  
Testing Procedure ◽  
Open Hole ◽  
Integrity Tests ◽  
Wellbore Strengthening ◽  
Fracture Gradient ◽  
Petroleum Development ◽  
First Time

Abstract Formation Integrity Tests (FIT) or Leak-Off Tests (LOT) are common techniques to reduce the uncertainty in Fracture Gradient (FG) prediction for well planning, but are usually performed at the casing shoe. This article will discuss the first examples of open-hole LOT and FIT in Petroleum Development Oman (PDO), targeting depleted formations in water injector or oil producer wells. The data was used to justify continued drilling of slim wells with two casing strings, where otherwise three casing strings would be required, provided dynamic wellbore strengthening is applied. In addition, the concept of static wellbore strengthening was also trialed for the first time in Oman, using the hesitation squeeze testing procedure, by which the effective leak-off pressure was incrementally increased to match the maximum ECD required for cementing.

Navigating the Depleted Fracture Gradient During Operations: From Concept to Drilling, Open Hole FIT Management & Cementing

2021 ◽  
Author(s):  
Gerard O'Reilly ◽  
Alvin W. Chan
Keyword(s):  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Successful Outcome ◽  
Drilling Fluids ◽  
Operational Experience ◽  
Gas Industry ◽  
Lost Circulation ◽  
Open Hole ◽  
Remedial Work ◽  
Fracture Gradient

Abstract Depleted Fracture Gradients have been a challenge for the oil and gas industry during drilling and cementing operations for over 30 years. Yet, year after year, problems related to lost circulation, borehole instability (low mud weight due a low fracture gradient), and losses during cementing operations leading to NPT and remedial work continue to rank as some of the top NPT events that companies face. This paper will demonstrate how the geomechanical modeling, well execution and remedial strengthening operations should be implemented to provide for a successful outcome. The use of a Fracture Gradient (FG) framework will be discussed, and the use of a negotiated fracture gradient will highlight how the fracture gradient can be changed during operations. This paper will also show actual examples from Deepwater operations that have successfully executed a detailed borehole strengthening program. Through our offset studies and operational experience, we will provide a format for navigating complex depleted drilling issues and show an example on recovering from low fracture gradients. This paper will demonstrate (1) how our framework facilitated multi-disciplinary collaborative discussion among our subsurface and well engineering communities; (2) how the impacts of drilling fluids and operational procedures can change this lost circulation threshold; and (3) how our negotiated FG approach has successfully delivered wells drilled in narrow margins.

Overcoming Lost Circulation Risks in Low Fracture Gradient Formations with a New Tailored Spacer System

2021 ◽  
Author(s):  
Kory Hugentobler ◽  
Joseph M. Shine ◽  
Alejandro De La Cruz Sasso ◽  
Abdulmalek Shamsan ◽  
Sandip Patil ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Performance Testing ◽  
Lost Circulation ◽  
Oil And Gas Operations ◽  
Primary Cementing ◽  
Isolation Requirements ◽  
And Performance ◽  
Wellbore Strengthening ◽  
Placement Success ◽  
Fracture Gradient

Abstract In certain regions of oil and gas operations, lost circulation is a common occurrence, especially when a majority of the openhole exposed during primary cementing is carbonate-based formations. This can lead to lost circulation risks in most applications. To overcome lost circulation risks during primary cementing, a new tailored spacer system shows to improve the cement placement success. The manuscript discusses the quality assurance and performance testing with field cases demonstrating the value contributions of the spacer for achieving zonal isolation requirements as well as the top of cement objectives. The work efforts presented shows a spacer meeting and sometimes showing incremental wellbore strengthening in comparison to the published literature for existing available spacers used to overcome similar lost circulation risks.

Failure Analysis of the Tripping Operation and its Impact on Well Control

2015 ◽  
Author(s):  
Majeed Abimbola ◽  
Faisal Khan ◽  
Vikram Garaniya ◽  
Stephen Butt
Keyword(s):  
Human Error ◽  
Integrated Control ◽  
Fault Tree ◽  
Fault Tree Analysis ◽  
Well Control ◽  
Lost Circulation ◽  
Critical Elements ◽  
Open Hole ◽  
Critical Components ◽  
The Cost

As the cost of drilling and completion of offshore well is soaring, efforts are required for better well planning. Safety is to be given the highest priority over all other aspects of well planning. Among different element of drilling, well control is one of the most critical components for the safety of the operation, employees and the environment. Primary well control is ensured by keeping the hydrostatic pressure of the mud above the pore pressure across an open hole section. A loss of well control implies an influx of formation fluid into the wellbore which can culminate to a blowout if uncontrollable. Among the factors that contribute to a blowout are: stuck pipe, casing failure, swabbing, cementing, equipment failure and drilling into other well. Swabbing often occurs during tripping out of an open hole. In this study, investigations of the effects of tripping operation on primary well control are conducted. Failure scenarios of tripping operations in conventional overbalanced drilling and managed pressure drilling are studied using fault tree analysis. These scenarios are subsequently mapped into Bayesian Networks to overcome fault tree modelling limitations such s dependability assessment and common cause failure. The analysis of the BN models identified RCD failure, BHP reduction due to insufficient mud density and lost circulation, DAPC integrated control system, DAPC choke manifold, DAPC back pressure pump, and human error as critical elements in the loss of well control through tripping out operation.

Case Studies and Best Practices for Installation of Open Hole Multistage Completion Systems in Wells Drilled Underbalanced

2014 ◽  
Author(s):  
John Bonar ◽  
D.J. Snyder ◽  
Brittany Dale Miller ◽  
Lonnie Jeffers
Keyword(s):  
Best Practices ◽  
Case Studies ◽  
Open Hole

Managed-Pressure Cementing in HPHT Well with Very Narrow Operating Pressure Window

2021 ◽  
Author(s):  
David Salinas Sanchez ◽  
Mario Noguez Lugo ◽  
Oscar Zamora Torres ◽  
Cuauhtemoc Cruz Castillo ◽  
Moises Muñoz Rivera ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Stopping Time ◽  
Operating Pressure ◽  
Cement Slurry ◽  
Working Pressure ◽  
Lost Circulation ◽  
Main Challenge ◽  
Fiber Technology ◽  
Open Hole ◽  
Reverse Circulation

Abstract A 7-in. liner was successfully cemented in the south east region of Mexico at 7530 m MD despite significant pressure and temperature challenges. The entire 1,370-m, 8.5" open hole section needed cement coverage and isolation to test several intervals. The challenge of the ultranarrow working pressure window was overcome by using managed pressure cementing (MPC) along with lost circulation solutions for the cement slurry and spacer. Due to the narrow pressure window (0.05 g/cc density gradient), mud losses could not be avoided during the cementing job. To limit and manage losses, an MPC placement technique was proposed, in conjunction with using lost circulation fiber technology in the cement slurry and spacer. After addressing the losses and narrow working pressure window, the next main challenge was the extremely high temperature (Bottom hole static temperature of 171°C). Extensive lab testing provided the fluid solution: HT formulations for cement slurry and spacer to maintain stability and rheology for placement and management of equivalent circulating density and set cement properties for long-term zonal isolation. After the liner was run to bottom, the mud density was homogenized from 1.40 g/cc to 1.30 g/cc (pore pressure: 1.38 g/cc). During this process, 32.5 m3 of mud was lost to the formation. During the previous circulation, the backpressure required to maintain the equivalent circulation density (ECD) above pore pressure, which was calculated and validated resulting in 1,100 psi annulus surface pressure (close to the limit of the equipment capacity) during the stopping time. The cementing job was pumped flawlessly with only 10 m3 of mud loss at the end of the job. During reverse circulation, contaminated spacer at surface indicated no cementing fluid had been lost to the formation and adequate open-hole coverage. The liner was successfully pressure tested to 4,500 psi, and cement logs showed that the cement had covered the open hole completely. MPC is not a conventional cementing technique. After the successful result on this job and subsequent operations, this technique is now being adopted to optimize cementing in even deeper wells in Mexico, where losses during cementing operations in the past had modified or limited the whole well construction and designed completion, and production of the well.

The evolution of lost circulation prevention and mitigation based on wellbore strengthening theory: A review on experimental issues

2022 ◽  
pp. 110149
Author(s):  
Seyed Morteza Mirabbasi ◽  
Mohammad Javad Ameri ◽  
Mortadha Alsaba ◽  
Mohsen Karami ◽  
Amir Zargarbashi
Keyword(s):  
Lost Circulation ◽  
Wellbore Strengthening

Use Of Fiber Materials to Mitigate Lost Circulation During Cementing Operations in Turkmenistan

2021 ◽  
Author(s):  
Amanmammet Bugrayev ◽  
Svetlana Nafikova ◽  
Salim Taoutaou ◽  
Guvanch Gurbanov ◽  
Maksatmyrat Hanov ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Control Treatment ◽  
Cement Slurry ◽  
Lost Circulation ◽  
Innovative Materials ◽  
Primary Cementing ◽  
Fit For Purpose ◽  
Fiber Materials ◽  
Fracture Gradient ◽  
Application Requirements

Abstract Lost circulation in depleted sands during a primary cementing job is a serious problem in Turkmenistan. The uncertainty in formation pressure across these sands increases the risk of losses during drilling and cementing, which results in remedial operations and nonproductive time. The need to find a fit-for-purpose lost circulation solution becomes even more critical in an environment with narrow pore pressure-to-fracture gradient, where each cement job with losses compromises the downhole well integrity. An engineered lost circulation solution using innovative materials in the cement slurry was carefully assessed and qualified in the laboratory for each case to optimize the formulation. The lost circulation control treatment combines specialized engineered fibers with sized bridging materials to increase the effectiveness of treatment, formulated and added to the cement slurries based on the slurry solids volume fraction (SVF). Cement slurries with low SVF were treated with higher concentrations of the product and slurries with high SVF used lower concentrations. More than 50 jobs were performed with cement slurries designed at various densities and SVF up to 58% and using this advanced lost circulation material (LCM) to mitigate losses during cementing. Field experience showed positive results, where the differential pressure up to 2,800 psi was expected during cementing operation. A local database, generated based on the design and development work performed, enabled improved decision-making for selection and LCM application requirements for subsequent jobs and development of a lost circulation strategy. The mitigation plan was put in place against losses in critical sections and depleted sand formations in Turkmenistan. It assisted in meeting the cement coverage requirements on numerous occasions, improving overall the integrity of the wells and thus, was considered to be a success. This paper provides insight of this advanced LCM, its application in cement slurries, the logic behind the developed loss circulation strategy, and the high success rate of its implementation. Three case histories are presented to demonstrate the strategy and results.

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.

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