Study of Ultrasonic Logs and Seepage Potential on Sandwich Sections Retrieved from a North Sea Production Well

2021 ◽  
pp. 1-15
Author(s):  
Hans Joakim Skadsem ◽  
Dave Gardner ◽  
Katherine Beltrán Jiménez ◽  
Amit Govil ◽  
Guillermo Obando Palacio ◽  
...  
Keyword(s):  
Gas Flow ◽  
Fluid Migration ◽  
Production Well ◽  
Offshore Production ◽  
Extensive Test ◽  
Sustained Casing Pressure ◽  
Zonal Isolation ◽  
Seepage Characteristics ◽  
Casing Pressure ◽  
Well Cement

Summary Important functions of well cement are to provide zonal isolation behind casing strings and to mechanically support and protect the casing. Experience suggests that many wells develop integrity problems related to fluid migration or loss of zonal isolation, which often manifest themselves in sustained casing pressure (SCP) or surface casing vent flows. Because the characteristic sizes of realistic migration paths are typically only on the order of tens of micrometers, detecting, diagnosing, and eventually treating migration paths remain challenging problems for the industry. As part of the recent abandonment operation of an offshore production well, sandwich joints comprising production casing, annulus cement, and intermediate casing were cut and retrieved to surface. Two of these joints were subjected to an extensive test campaign, including surface relogging, chemical analyses, and seepage testing, to better understand the ultrasonic-log response and its potential connection to rates of fluid migration. One of the joints contained an apparently well-defined top of cement (TOC) with settled barite on top. Although the settled material initially provided a complete seal against gas flow, the sealing capability was irreversibly lost as part of subsequent testing. The two joints have effective microannuli sizes in the range of tens of micrometers, in agreement with previous reports on SCP buildup in wells. On a local scale, however, we observed significant variations in cement quality from both the log results and the seepage testing. Further, we found qualitatively very good correlations between seepage-test results and the log results for the bond between cement and casings. The best bonded cement was found directly above a production casing collar, where a short segment of well-bonded cement prevented measurable steady-state seepage of nitrogen. Additional tests involving internal pressurization of the production casing suggested that certain annular-seepage characteristics are well-described by an effective microannulus at the cement/casing interfaces. We consider the two sandwich joints to be highly representative and relevant for similar mature wells that are to be abandoned.

A Breakthrough Approach to Solve Shallow Gas Hazards in Corrosive Carbon Dioxide Wells

2021 ◽  
Author(s):  
Yi Li ◽  
Solim Ullah Mohammad ◽  
Wu chang Ai ◽  
Avinash Kishore Kumar ◽  
Lau Chee Hen ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Gas Flow ◽  
Shallow Gas ◽  
Security Issues ◽  
Sustained Casing Pressure ◽  
Zonal Isolation ◽  
Primary Cementing ◽  
Carbon Dioxide Co2 ◽  
Casing Pressure

Abstract In offshore Malaysia field, several development wells were drilled and cemented in 2019. The presence of shallow gas zone directly below the surface casing shoe posed a significant challenge to isolate shallow gas flow. A High presence of carbon dioxide (CO2) also increased the complexity of the cementing jobs by potentially corroding the set cement sheath. Wells with sustained casing pressure due to poor cementing jobs would causelosses to hydrocarbon reserves, while polluting aquifers with hydrocarbon and well security issues. It was crucial to prevent remedial cementing work, due to unnecessary and costly non-productive time. The objective of primary cementing is to achieve long term zonal isolation across the gas reservoir. A bespoke engineered cementing solution was successfully developed in order to provide a solution to assure long term zonal isolation for shallow gas flow. This paper will describe in detail about the cementing method, how it fits the well situation, the methodology in the slurry design, and thevalidation process in the lab with a novel, uncommon method in the industry, capped off by the post-cementing results analysis. This technology was proven as a solution for shallow gas well cementing and long-term zonal isolation, which is a great referencefor the cementing industry.

Implementation of Factory Cementing Concept in the High-Intensity Drilling Environment of Khazzan, Sultanate of Oman

2021 ◽  
Author(s):  
Emmanuel Therond ◽  
Yaseen Najwani ◽  
Mohamed Al Alawi ◽  
Muneer Hamood Al Noumani ◽  
Yaqdhan Khalfan Al Rawahi ◽  
...  
Keyword(s):  
Shallow Water ◽  
High Intensity ◽  
Sultanate Of Oman ◽  
Cement Slurry ◽  
Short Term ◽  
Lost Circulation ◽  
Well Integrity ◽  
Sustained Casing Pressure ◽  
Zonal Isolation ◽  
Casing Pressure

Abstract The Khazzan and Ghazeer gas fields in the Sultanate of Oman are projected to deliver production of gas and condensate for decades to come. Over the life of the project, around 300 wells will be drilled, with a target drilling and completion time of 42 days for a vertical well. The high intensity of the well construction requires a standardized and robust approach for well cementing to deliver high-quality well integrity and zonal isolation. The wells are designed with a surface casing, an intermediate casing, a production casing or production liner, and a cemented completion. Most sections are challenging in terms of zonal isolation. The surface casing is set across a shallow-water carbonate formation, prone to lost circulation and shallow water flow. The production casing or production liner is set across fractured limestones and gas-bearing zones that can cause A- and B-Annulus sustained casing pressure if not properly isolated. The cemented completion is set across a high-temperature sandstone reservoir with depletion and the cement sheath is subjected to very high pressure and temperature variations during the fracturing treatment. A standardized cement blend is implemented for the entire field from the top section down to the reservoir. This blend works over a wide slurry density and temperature range, has expanding properties, and can sustain the high temperature of the reservoir section. For all wells, the shallow-water flow zone on the surface casing is isolated by a conventional 11.9 ppg lightweight lead slurry, capped with a reactive sodium silicate gel, and a 15.8 ppg cement slurry pumped through a system of one-inch flexible pipes inserted in the casing/conductor annulus. The long intermediate casing is cemented in one stage using a conventional lightweight slurry containing a high-performance lost circulation material to seal the carbonate microfractures. The excess cement volume is based on loss volume calculated from a lift pressure analysis. The cemented completion uses a conventional 13.7 - 14.5 ppg cement slurry; the cement is pre-stressed in situ with an expanding agent to prevent cement failure when fracturing the tight sandstone reservoir with high-pressure treatment. Zonal isolation success in a high-intensity drilling environment is assessed through key performance zonal isolation indicators. Short-term zonal isolation indicators are systematically used to evaluate cement barrier placement before proceeding with installing the next casing string. Long-term zonal isolation indicators are used to evaluate well integrity over the life of the field. A-Annulus and B-Annulus well pressures are monitored through a network of sensors transmitting data in real time. Since the standardization of cementing practices in the Khazzan field short-term job objectives met have increased from 76% to 92 % and the wells with sustained casing pressure have decreased from 22 % to 0%.

Laboratory Visualization of Gravity Fluid Displacement in Well Annulus Affected by Sustained Casing Pressure

2015 ◽  
Author(s):  
Efecan Demirci ◽  
Andrew K. Wojtanowicz
Keyword(s):  
Injection Rate ◽  
Fluid Displacement ◽  
Two Fluids ◽  
Gas Leak ◽  
Displacement Experiments ◽  
Sustained Casing Pressure ◽  
Petroleum Wells ◽  
Casing Pressure ◽  
Well Cement ◽  
Synthetic Clay

Sustained Casing Pressure (SCP) in petroleum wells poses environmental risk and needs to be removed using either downhole intervention or annular intervention methods. The latter method involves displacing the annular fluid above the top of the gas-leaking well cement with a heavy fluid to increase the hydrostatic pressure and stop the gas leak. Past field applications of the method failed — most likely due to incompatibility of the two fluids. In this study, a see-through scaled-down hydraulic analog of the well’s annulus was designed and used for video-taped displacement experiments with clear synthetic-clay muds and heavy (kill) fluids. The results show that only immiscible hydrophobic kill fluids provide effective displacement. The study demonstrates importance of controlled injection of the kill fluid to set out efficient buoyant settling and prevent initial dispersion. A side- (versus top-) injection geometry and the injection rate data are analyzed to develop empirical correlation of maximum injection rate for a given properties of the two fluids.

Risk and Remediation of Irreducible Casing Pressure at Petroleum Wells

2014 ◽  
pp. 155-180 ◽  
Author(s):  
Andrew K. Wojtanowicz
Keyword(s):  
Oil Well ◽  
Gas Migration ◽  
Excessive Pressure ◽  
Wet Gas ◽  
Regulatory Approach ◽  
Sustained Casing Pressure ◽  
Small Cracks ◽  
Petroleum Wells ◽  
Casing Pressure ◽  
Well Cement

Oil well cement problems such as small cracks or channels may result in gas migration and lead to irreducible pressure at the casing head. Irreducible casing pressure also termed, Sustained Casing Pressure (SCP) is hazardous for a safe operation and the affected wells cannot be terminated without remedial operations. It is believed that even very small leaks might lead to continuous emissions of gas to the atmosphere. In the chapter, the author describes physical mechanisms of irreducible casing pressure and qualifies the associated risk by showing statistical data from the Gulf of Mexico and discussing the regulatory approach. This chapter also introduces a new approach to evaluate risk of casing pressure by computing a probable rate of atmospheric emissions from wells with failed casing heads resulting from excessive pressure. Also presented is a new method for assessing potential for self-plugging of such wells flowing wet gas as the gas migration channels could be plugged off by the condensate.

Comparative experimental evaluation of drilling fluid contamination on shear bond strength at wellbore cement interfaces

2014 ◽  
Vol 11 (6) ◽  
pp. 597-604 ◽  
Author(s):  
Mileva Radonjic ◽  
Arome Oyibo
Keyword(s):  
Bond Strength ◽  
Shear Bond Strength ◽  
Oil And Gas ◽  
Drilling Fluid ◽  
Cement Slurry ◽  
Geothermal Wells ◽  
Sustained Casing Pressure ◽  
Zonal Isolation ◽  
Casing Pressure ◽  
The Impact

Wellbore cement has been used to provide well integrity through zonal isolation in oil and gas wells as well as geothermal wells. Failures of wellbore cement result from either or both: inadequate cleaning of the wellbore and inappropriate cement slurry design for a given field/operational application. Inadequate cementing can result in creation of fractures and microannuli, through which produced fluids can migrate to the surface, leading to environmental and economic issues such as sustained casing pressure, contamination of fresh water aquifers and, in some cases, well blowout. To achieve proper cementing, the drilling fluid should be completely displaced by the cement slurry, providing clean interfaces for effective bond. This is, however, hard to achieve in practice, which results in contaminated cement mixture and poor bonds at interfaces. This paper reports findings from the experimental investigation of the impact of drilling fluid contamination on the shear bond strength at the cement-formation and the cement-casing interfaces by testing different levels of contamination as well as contaminations of different nature (physical vs. chemical). Shear bond test and material characterization techniques were used to quantify the effect of drilling fluid contamination on the shear bond strength. The results show that drilling fluid contamination is detrimental to both cement-formation and cement-casing shear bond strength.

Lessons Learned and Case Studies of Overcoming Sustained Casing Pressure in Extended-Reach Wells

2021 ◽  
Author(s):  
Svetlana Nafikova ◽  
Yulia Ramazanova ◽  
Alexander Muslimov ◽  
Ilshat Akhmetzianov ◽  
Bipin Jain ◽  
...  
Keyword(s):  
Best Practices ◽  
Caspian Sea ◽  
The Self ◽  
Self Healing ◽  
Effective Solution ◽  
Pressure Buildup ◽  
Cement System ◽  
Sustained Casing Pressure ◽  
Zonal Isolation ◽  
Casing Pressure

Abstract Achieving zonal isolation for the lifetime of oil and gas wells is crucial for well integrity. Poor zonal isolation can detrimentally affect well economics and increase safety-related risks because of pressure buildup with unpredictable consequences. Additional local regulations prohibiting production of a well with positive pressure in the annulus made sustained casing pressure a major challenge for operators in the North Caspian Sea. An innovative cost-effective solution was required to resolve this challenge. Historical well analysis proved that previously applied cementing approaches were ineffective. Several modifications were required to define the effective solution. Implemented changes included revision of the casing setting depth, optimization of the drilling fluids and spacer formulations, and implementation of the self-healing expanding cement. Carefully engineered placement of the self-healing cement system was the key to success. If cracks or microannuli occur and hydrocarbons reach the cement and flow through the cracks, the system has the capability to repair itself, thus restoring integrity of the cement sheath without external intervention. This technology has been used in 11 extended reach wells in two fields with excellent results. The collaborative approach with drilling engineers eliminated the challenging sustained casing pressure issue in two major offshore fields in North Caspian Sea. In addition to the existing cementing best practices available in industry for mud removal efficiency enhancement and successful cement placement, the newly implemented methodology included potential requirements for well trajectory adjustments, implementation of the real-time control during cementing job execution, engineered placement and optimization of the self-healing expanding cement system formulation, and a specifically developed "initially required" bleedoff schedule that allows acceleration of the self-remediation cement capability. The self-healing cement was designed with low Young's modulus for maximum flexibility. Expanding additives were also incorporated into the design to minimize the risk of set cement integrity failure due to microdebonding from bulk shrinkage after setting. Adherence to the mutually developed flowchart for the drilling and cementing stages improved the zonal isolation of the critical hydrocarbon zones in the extended reach wells and increased the success ratio of the wells with no pressure buildup from 30% to almost 100% within the last 5 years. As a result, the self-healing cement technology and developed approach, which is discussed in this paper, have become the standard for both fields for all future wells. The complex engineering approach described in this paper expands the existing best practices in the industry for zonal isolation improvement of the extended reach wells and provides a new effective solution for eliminating sustained casing pressure problems. The design strategy, execution, evaluation, and results for two sample wells are discussed in detail to help to guide future engineering and operational activities around the world.

Advanced Remedial Hydraulic Isolation by Perforate and Wash Technique

2021 ◽  
Author(s):  
Andrey Yugay ◽  
Hamdi Bouali Daghmouni ◽  
Andrey Nestyagin ◽  
Fouad Abdulsallam ◽  
Annie Morales ◽  
...  
Keyword(s):  
Time Pressure ◽  
Main Role ◽  
Cement Slurry ◽  
Accelerated Corrosion ◽  
Sustained Casing Pressure ◽  
Zonal Isolation ◽  
Cap Rock ◽  
Primary Cementing ◽  
Two Phases ◽  
Casing Pressure

Abstract Well Cementing can be divided into two phases – primary and remedial cementing. Primary cementing may have 3 functions: casing support, zonal isolation and casing protection against corrosion. First two functions are commonly recognized while the third one might be a point of discussion, as the full casing coverage with 100% clean cement is not something common in most of the fields. In fact, poorly cemented areas of the casing may become negatively charged and create a zones of accelerated corrosion rate. This paper is about main role of cementing - zonal isolation. The process of primary cementing assumes that cement slurry is being pumped into the casing and displaced outside. After wait on cement time (WOC) it becomes hard, develops compressive strength and creates impermeable seal that ensures hydraulic isolation. Old and well-known technique, it still remains one of the most challenging rig operations. It is unlikely to find a service company that would guarantee 100% cement displacement behind the casing all the way from top to bottom. Main challenges in this region are quiet common for many other fields – displacement in deviated sections, losses before and during cementing, exposure to pressure during cement settling. In case the main target is not achieved (no hydraulic isolation behind the casing) – we may observe behind casing communications resulting in sustainable pressures in casing-casing annuluses. In this situation the remedial cementing takes place. It's function is to restore isolation so the cement can work as a barrier that seals off the pressure source. Despite of the good number of sealants available on the market (time, pressure, temperature activated) that can be injected from surface to cure this casing-casing pressure, Company prefers not to do so unless there is a proven injectivity capability that would allow for the sealant to reach deep enough, to protect aquifers in case of outer casing corrosion. Otherwise that would be just a ‘masking" the pressure at surface. Therefore in general Company prefers rig intervention to cure the pressure across the cap rock in between the aquifers and the reservoir. Those aquifers are illustrated on the Figure 1 below: More details on Company casing design, cement evaluation issues, sustained casing pressure phenomena and challenges have been mentioned previously [Yugay, 2019].

scholarly journals Fluid Migration Characterization of Full-scale Annulus Cement Sections Using Pressure-Pulse-Decay Measurements

2021 ◽  
pp. 1-30
Author(s):  
Hans Joakim Skadsem
Keyword(s):  
Steady State ◽  
Pressure Pulse ◽  
Test Procedure ◽  
Full Scale ◽  
Fluid Migration ◽  
Transient Pressure ◽  
Bottom Part ◽  
Sustained Casing Pressure ◽  
Interference Tests ◽  
Casing Pressure

Abstract Fluid migration behind casings is a well integrity problem that can result in sustained casing pressure, undetected leaks to the environment and potentially very challenging remediation attempts. Understanding the geometric dimensions and extent of annular migration paths is important for diagnosing and effectively treating fluid migration and sustained casing pressure problems in wells. We report measurements of permeability and micro-annuli in two full-scale cemented annulus test sections using a combination of transient pressure-pulse-decay and steady state seepage measurements. One of these sections is a cemented 9 5/8-in and 13 3/8-in casing section from a 30 years old Norwegian North Sea production well. For both sections we find equivalent micro-annulus sizes that are within the range of effective wellbore permeabilities based on sustained casing pressure records and previous vertical interference tests in wells. The test sections display measurable axial permeability variations with the bottom part of these vertical sections having the lower permeability. For the retrieved casing section the change corresponds to the transition through the top of cement which is nearly in the middle of the test section. Increasing internal casing pressure is found to slightly reduce the equivalent micro-annulus size, indicative of fracture-like response of the migration paths. A perceived benefit of the transient test procedure discussed herein is a significantly faster permeability characterization especially within low-permeable sections where it is otherwise difficult to establish steady state flow conditions.

Novel collaborative P&A campaign using inflatable packers and bismuth alloy plugs

2021 ◽  
Vol 61 (2) ◽  
pp. 536
Author(s):  
Adam Bensaied ◽  
George Farag ◽  
Jeff Fulks
Keyword(s):  
Gas Flow ◽  
Cost Savings ◽  
Significant Cost ◽  
North West ◽  
Sustained Casing Pressure ◽  
Bismuth Alloy ◽  
Casing Pressure ◽  
Cement Plug ◽  
Lengthy Process

Chevron Australia, a leading O&G operator on the Australian North West Shelf, executed a plug and abandonment (P&A) campaign where 34 wells (19 offshore and 15 onshore) incorporated a novel bismuth alloy barrier system to the traditional cement plug. The challenge of isolating shallow gaseous zones that cause sustained casing pressure and free gas flow to surface behind the production casing was overcome by this new innovative use of collaborative technologies to provide an optimised P&A solution. The offshore/onshore P&A campaign was completed successfully with significant cost savings, eliminating the lengthy process of section milling more than 100ft of casing on each well, providing a long-term bismuth alloy barrier in the well and eliminating the potential need to reenter the well later due to a leaking cement plug.

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