Evaluation Method for Cement Sheath Sealing Failure Under Sustained Casing Pressure

2019 ◽  
Vol 55 (1) ◽  
pp. 93-104 ◽  
Author(s):  
Jing Zeng ◽  
Deli Gao ◽  
Yanbin Wang ◽  
Jun Fang
Keyword(s):  
Evaluation Method ◽  
Sustained Casing Pressure ◽  
Cement Sheath ◽  
Sealing Failure ◽  
Casing Pressure

Mechanically Enhanced Cementing: Mitigation Against Sustained Casing Pressure in Highly Stressed Downhole Environment, Offshore Niger Delta

2021 ◽  
Author(s):  
Ilyas Abdulsalaam ◽  
Chibuzor Amos ◽  
Grace Ahabike ◽  
Rebecca Ejukorlem-Okusi
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Niger Delta ◽  
Cement Slurry ◽  
Element Analysis ◽  
Well Production ◽  
Sustained Casing Pressure ◽  
Remaining Capacity ◽  
Cement Sheath ◽  
Casing Pressure

Abstract A major Exploration and Production (E & P) company was posed with a challenge of sustained casing pressure in over 85% of the wells drilled in one of the fields in the Offshore Niger Delta. Sustained casing pressure occurs when the annular seal is damaged and a path is created for the formation pressure to reach the surface, and the pressure in the annulus rebuilds after being bled down. When cementing in such an environment, operators have the following objectives: Placing a cement sheath with increased capability to survive future downhole stress events.Achieving effective mud removal.Gaining the benefits of a react and respond sheath design.Providing a long productive life for the wellbore. To develop a cement system that would achieve and maintain isolation throughout the life of the well, an advanced cement technology was required. This advanced cement technology involved Finite Element Analysis (FEA) to model the effects of stresses from well operations on the cement sheath. This analysis takes into consideration well configuration, formation properties, casing properties, cement properties and operational loads and predicts the remaining capacities of the cement sheath. The remaining capacity is used to measure how much a cement sheath is stressed. After simulating the effect of downhole stresses on a cement sheath, a mechanically enhanced cement slurry was designed to meet the recommendations of the model and provide a cement sheath with improved remaining capacity. This paper presents the successful mechanically enhanced slurry design, job design, planning and execution on the production section of the well after a Finite Element Analysis was conducted. Post job conditions such as good cement bonds across cemented areas, well production without inter-zonal communication and no annular pressure build up in over 8 years have proven the success of the design and the procedure implemented in these challenging well bore environments. The success of this well has been applied to two additional wells.

scholarly journals Impact of Casing Eccentricity on Cement Sheath

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2557 ◽  
Author(s):  
Kui Liu ◽  
Deli Gao ◽  
Arash Taleghani
Keyword(s):  
Stress Distribution ◽  
Shale Gas ◽  
Radial Stress ◽  
Circumferential Stress ◽  
Horizontal Wells ◽  
Gas Production ◽  
Gas Wells ◽  
Sustained Casing Pressure ◽  
Cement Sheath ◽  
Casing Pressure

Sustained casing pressure (SCP) in shale gas wells caused by cement sheath failure can have serious impacts on safe and efficient gas production. Considering the fact that horizontal wells are widely used for production from shale, the cementing quality and casing centricity is barely ensured in these wells. Among other indications, the casing eccentricity is identified very often in wells with SCP problems in the Sichuan field in China. Hence, the objective of this study is to analyze the effect of the casing eccentricity on the integrity of the cement sheath. To better understand stress distribution in eccentric cement sheaths, an analytical model is proposed in this paper. By comparing the results of this model with the one’s with centric casing, the impacts of the casing eccentricity on the integrity of the cement sheath is analyzed. During fracturing treatments, the casing eccentricity has a little effect on stress distribution in the cement sheath if the well is well cemented and bonded to the formation rock. However, on the contrary, the casing eccentricity may have serious effects on stress distribution if the cementing is done poorly. The debonding of casing–cement–formation interfaces can significantly increase the circumferential stress in the cement sheath. At the thin side of the cement sheath, the circumferential stress could be 2.5 times higher than the thick side. The offset magnitude of the casing eccentricity has little effect on the radial stress in the cement sheath but it can significantly increase the shear stress. We found that the risk of cement failure may be reduced by making the casing string more centralized, or increasing the thickness of the casing. The results provide insights for design practices which may lead to better integrity in shale gas wells.

Avoiding Sustained Casing Pressure in Gas wells using Self Healing Cement

2011 ◽  
Author(s):  
Salim Taoutaou ◽  
Jorge Andres Vargas Bermea ◽  
Pietro Bonomi ◽  
Bassam Elatrache ◽  
Christian Pasturel ◽  
...  
Keyword(s):  
Self Healing ◽  
Gas Wells ◽  
Sustained Casing Pressure ◽  
Casing Pressure

Sustained Casing Pressure Calculation of A Annulus Induced by Downhole Operation Load

2012 ◽  
Vol 430-432 ◽  
pp. 2067-2070
Author(s):  
Zhang Zhi ◽  
Tai Ping Xiao ◽  
Zheng Mao Chen ◽  
Tai He Shi
Keyword(s):  
Internal Pressure ◽  
Safety Evaluation ◽  
Calculation Model ◽  
Extrusion Force ◽  
External Diameter ◽  
Gas Well ◽  
Seal Failure ◽  
Theoretical Support ◽  
Sustained Casing Pressure ◽  
Casing Pressure

Currently the annulus pressure of gas well becomes more common, so the safe production of several wells has been seriously affected. The annulus pressure mechanism is relatively complex, and it can be approximately classified into annulus pressure induced by temperature effect, by ballooning effect and by leakage or seal failure etc. The article mainly focuses on the annulus pressure mechanism induced by ballooning effect and the corresponding calculation model. For the tubing column with two ends fixed and closed, when tubing internal pressure is larger than the external extrusion force, the external diameter of the tubing column balloons (i.e. ballooning effect). It reduces the annular volume between the tubing and the casing, and consequentially induces annulus pressure. Based on the fundamental theory of elastic-plastic mechanics, the tubing column is simplified into the thin walled cylinder so as to deduce the relation models between the internal pressure and its swell capacity and A annulus pressure value, which provide theoretical support for safety evaluation on annulus pressure and the next treatment program.

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.

Successful Remediation of Sustained Casing Pressures in Gas Cap Injector Wells with the Use of Flexible and Self Healing System

2021 ◽  
Author(s):  
Bipin Jain ◽  
Abhijeet Tambe ◽  
Dylan Waugh ◽  
Moises MunozRivera ◽  
Rianne Campbell
Keyword(s):  
Self Healing ◽  
Injection Wells ◽  
Coiled Tubing ◽  
Cement System ◽  
Sustained Casing Pressure ◽  
Casing Pressure ◽  
New Generation ◽  
Prudhoe Bay ◽  
Production Tubing

Abstract Several injection wells in Prudhoe Bay, Alaska exhibit sustained casing pressure (SCP) between the production tubing and the inner casing. The diagnostics on these wells have shown communication due to issues with casing leaks. Conventional cement systems have historically been used in coiled-tubing-delivered squeeze jobs to repair the leaks. However, even when these squeeze jobs are executed successfully, there is no guarantee in the short or long term that the annular communication is repaired. Many of these injector wells develop SCP in the range of 300-400 psi post-repair. It has been observed that the SCP development can reoccur immediately after annulus communication repair, or months to years after an injector well is put back on injection. Once SCP is developed the well cannot be operated further. A new generation of cement system was used to overcome the remedial challenge presented in these injector wells. This document provides the successful application of a specialized adaptive cement system conveyed to the problematic zone with the advantage of using coiled tubing equipment for optimum delivery of the remedial treatment.

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