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.

Application of Wellbore Strengthening Techniques in Carbonate Formation Solves Lost Circulation Challenges During Liner Running and Cementing

2021 ◽  
Author(s):  
Muneer Al Noumani ◽  
Younis Al Masoudi ◽  
Mohammed Al Mamari ◽  
Yaqdhan Al Rawahi ◽  
Mohammed Al Yaarubi ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Well Performance ◽  
Design Work ◽  
Lost Circulation ◽  
The North ◽  
Carbonate Formation ◽  
Zonal Isolation ◽  
Isolation Requirements ◽  
Wellbore Strengthening

Abstract For many years, the oil and gas industry has deployed techniques which enhance formation strength via the successful propping and plugging of induced fractures. Induced fracture sizes have been successfully treated using this method up to the 600 – 1,100-micron range. Static wellbore strengthening techniques are commonly deployed to cover 1,000 micron and all fracture size risks underneath. The deployment of wellbore strengthening techniques has historically been confined to permeable formations. In most cases, wellbore strengthening has been deployed to operationally challenging sand fracture gradients or, where boundaries are pushed, lower ranges of permeability, such as silts. The subject of wellbore strengthening in shales or carbonates to this day, remains a challenge for the industry, with very few documented success stories or evidence of sustained ability to enhance fracture gradient across a drilling campaign. This paper covers the history of lost circulation events which have been reported in the Khazzan/Ghazeer field in the carbonate Habshan formation. It also describes the design changes which were introduced to strengthen the rock and enable circulation/returns, during liner cementation. The design work built on experience applying wellbore strengthening techniques in carbonates in the Norwegian sector of the North Sea. This work is also summarized in this paper. The Habshan carbonate formation in Oman presents a lost circulation challenge through an ‘induced’ fracture risk. Since the beginning of the drilling campaign in the Khazzan/Ghazeer field, the Habshan formation has repeatedly experienced induced mud losses during well activities such as liner running, mud conditioning with liner on bottom and cementing, when the formation is exposed to higher pressures, less so during drilling. The Habshan challenge in Oman has led to regular, significant lost circulation events during cement placement, adding operational cost and more importantly, presenting difficulties around meeting zonal isolation objectives. Through previous field experience in Norway, a set of criteria was developed to qualify a standard pill approach to carbonate strengthening. The currently deployed strategy is designed to address both the risk of induced fracture by propping and plugging (wellbore strengthening) and provide some ability to seal natural fractures which are often encountered with carbonates, or similarly flawed rocks. The strategy deployed aims to cover these two risks with a blanket approach to lost circulation risk in carbonates. The success of this approach is demonstrated using well performance data from a total of 43 wells drilled before and after the introduction of the wellbore strengthening strategy. As it was initially assumed that wellbore strengthening could not be applied to carbonate formations, other techniques had been tried to prevent lost circulation. Those techniques provided mixed results. Since the implementation of wellbore strengthening significant improvements in achieving zonal isolation requirements and reducing fluid losses have been documented.

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.

Obtaining Zonal Isolation in Geothermal Wells

2021 ◽  
Author(s):  
Allam Putra Rachimillah ◽  
Cinto Azwar ◽  
Ambuj Johri ◽  
Ahmed Osman ◽  
Eric Tanoto
Keyword(s):  
Best Practices ◽  
Oil And Gas ◽  
Lessons Learned ◽  
Free Fluid ◽  
High Heating Rate ◽  
Lost Circulation ◽  
Geothermal Well ◽  
Geothermal Wells ◽  
Zonal Isolation ◽  
Primary Cementing

Abstract Cementing is one of the sequences in the drilling operations to isolate different geological zones and provide integrity for the life of the well. As compared with oil and gas wells, geothermal wells have unique challenges for cementing operations. Robust cementing design and appropriate best practices during the cementing operations are needed to achieve cementing objectives in geothermal wells. Primary cementing in geothermal wells generally relies on a few conventional methods: long string, liner-tieback, and two-stage methods. Each has challenges for primary cementing that will be analyzed, compared, and discussed in detail. Geothermal wells pose challenges of low fracture gradients and massive lost circulation due to numerous fractures, which often lead to a need for remedial cementing jobs such as squeeze cementing and lost circulation plugs. Special considerations for remedial cementing in geothermal wells are also discussed here. Primary cement design is critical to ensure long-term integrity of a geothermal well. The cement sheath must be able to withstand pressure and temperature cycles when steam is produced and resist corrosive reservoir fluids due to the presence of H2S and CO2. Any fluid trapped within the casing-casing annulus poses a risk of casing collapse due to expansion under high temperatures encountered during the production phase. With the high heating rate of the geothermal well, temperature prediction plays an important part in cement design. Free fluid sensitivity test and centralizer selection also play an important role in avoiding mud channeling as well as preventing the development of fluid pockets. Analysis and comparison of every method is described in detail to enable readers to choose the best approach. Massive lost circulation is very common in surface and intermediate sections of geothermal wells. On numerous occasions, treatment with conventional lost-circulation material (LCM) was unable to cure the losses, resulting in the placement of multiple cement plugs. An improved lost circulation plug design and execution method are introduced to control massive losses in a geothermal environment. In addition, the paper will present operational best practices and lessons learned from the authors’ experience with cementing in geothermal wells in Indonesia. Geothermal wells can be constructed in different ways by different operators. In light of this, an analysis of different cementing approaches has been conducted to ensure robust cement design and a fit-for-purpose cementing method. This paper will discuss the cementing design, equipment, recommendations, and best available practices for excellence in operational execution to achieve optimal long-life zonal isolation for a geothermal well.

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.

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.

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.

Next Generation Oilfield on-Site Trace Chemicals Analysis by SERS

2021 ◽  
Author(s):  
Zhengwei Liu ◽  
Sankaran Murugesan ◽  
Sunder Ramachandran ◽  
Peng Jin
Keyword(s):  
Oil And Gas ◽  
Production Systems ◽  
Analytical Techniques ◽  
Chemical Additives ◽  
Factors Affecting ◽  
Oil And Gas Operations ◽  
Active Nature ◽  
Laboratory Procedures ◽  
Trace Chemicals ◽  
And Performance

Abstract Accurate and precise monitoring of chemical additives in oilfield brine is an important aspect of oil and gas operations towards corrosion control and flow assurance. Many operators are required to monitor the residual concentrations of chemical additives in production systems at specific locations to monitor and troubleshoot factors affecting chemical deliverability and performance. However, residual measurements are extremely problematic due to many factors, including the surface active nature of the chemicals and high ionic strength of the brine. The error on residual measurements can often be over 100%. Residual measurement typically requires the collection of a water sample, which often needs to be transported to a centralized analytical laboratory. Analytical techniques used to measure residuals are based on several combinations of separation (e.g. chromatography, liquid-liquid extraction, etc.) and detection (e.g. various forms of spectroscopy). However, most of these methods lack portability and require tedious laboratory procedures located off-site. The current paper describes a nanotechnology-enabled Raman spectroscopy method developed and tested for monitoring chemical inhibitor residuals. Development of this technology with handheld instrumentation provides better detection and quantification of chemical additives in the field and reduces time and cost compared to sending samples to off-site laboratories for data collection.

Investigation on the Effect of Mud Additives on the Gelation Performance of PAM/PEI System for Lost Circulation Control

2021 ◽  
Author(s):  
Mohamed Shamlooh ◽  
Ahmed Hamza ◽  
Ibnelwaleed A. Hussein ◽  
Mustafa S. Nasser ◽  
Saeed Salehi
Keyword(s):  
Storage Modulus ◽  
Oil And Gas ◽  
Loss Modulus ◽  
Drilling Fluid ◽  
Gelation Time ◽  
Drilling Fluids ◽  
Lost Circulation ◽  
Reservoir Conditions ◽  
Induced Fractures ◽  
Wellbore Strengthening

Abstract Lost circulation is one of the most common problems in the drilling of oil and gas wells where mud escapes through natural or induced fractures. Lost circulation can have severe consequences from increasing the operational cost to compromising the stability of wells. Recently, polymeric formulations have been introduced for wellbore strengthening purposes where it can serve as Loss Circulation Materials (LCMs) simultaneously. Polymeric LCMs have the potential to be mixed with drilling fluids during the operation without stopping to avoid non-productive time. In this study, the significance of most common conventional mud additives and their impact on the gelation performance of Polyacrylamide (PAM) / Polyethyleneimine (PEI) has been investigated. Drilling fluid with typical additives has been designed with a weight of 9.6 ppg. Additives including bentonite, barite, CarboxyMethylCellulose (CMC), lignite, caustic soda, desco, and calcium carbonate has been studied individually and combined. Each additive is mixed with the polymeric formulation (PAM 9% PEI 1%) with different ratios, then kept at 130°C for 24 hrs. Rheological performance of the mature gel has been tested using parallel plate geometry, Oscillatory tests have been used to assess the storage Modulus and loss modulus. Moreover, the gelation profile has been tested at 500 psi with a ramped temperature to mimic the reservoir conditions to obtain the gelation time. The gelation time of the polymer-based mud was controllable by the addition of a salt retarder (Ammonium Chloride), where a gelation time of more than 2 hours could be achieved at 130°C. Laboratory observations revealed that bentonite and CMC have the most effect as they both assist in producing stronger gel. While bentonite acts as a strengthening material, CMC increases the crosslinking network. Bentonite has successfully increased the gel strength by 15% providing a storage modulus of up to 1150 Pa without affecting the gelation time. This work helps in better understanding the process of using polymeric formulations in drilling activities. It provides insights to integrate gelling systems that are conventionally used for water shut-off during the drilling operation to replace the conventional loss circulation materials to provide a higher success rate.

Sign in / Sign up

Export Citation Format

Share Document