Cementing Practices to Solve Well Integrity Challenges of Ultra Deep High Temperature Wells in Western China

Guo, Yabin; Li, Xiaochun; Feng, Shiyu; Changduo, Zhang; Liu, Rui; Zhi, Zhang; Li, Tan; Peng, Guo; Wang, Rui; Taoutaou, Salim; Lee, Junn Shyong

doi:10.2118/182967-ms

Cited by 3 publications

(1 citation statement)

References 14 publications

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“…5,28 For high-pressure gas wells in the Tarim oilfield, the formation pore pressure could reach up to 145 MPa; the construction pressure could reach over 160 MPa. 29 Currently, there is a lack of a cement sheath mechanical integrity test method and device that can simulate or restore the pressure level of the wellbore under such high-pressure conditions. The current test device also cannot simulate the instantaneous cooling process in the acid pressure process.…”

Section: Introductionmentioning

confidence: 99%

Experiment and failure mechanism of cement sheath integrity under development and production conditions based on a mechanical equivalent theory

Huang

et al. 2021

Energy Science & Engineering

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During their life cycle, high-pressure gas wells experience circulating working fluid, acid fracturing, blow off, and other development and production conditions. This may lead to the failure of the cement sheath integrity and result in sustained casing pressure (SCP). Therefore, we explored the failure types and mechanisms of the cement sheath using different wellbore operating procedures. In this study, we used the downhole packer as the demarcation point; the integrity of the cement sheath at the upper and lower parts of the packer was tested through a self-developed wellbore simulation device, which is based on the equivalent theory of cement sheath interface differential pressure. Results showed that the lower part of the single-layer cement sheath underwent compressive strength failure due to the pressure drop in the wellbore before perforation. Plastic deformation of the cement sheath occurred during acid fracturing.In addition, the cooling effect caused by the acid fracturing led to the bonding failure at the cement sheath's second interface. The double-layer cement sheath's inner-layer cement sheath was subjected to tensile failure -attributed to highpressure -and the outer-layer cement sheath maintained its integrity under the pressure changes. Considering the risk factors associated with integrity failure, we propose an engineering optimization plan in the study. The retest results showed that reducing the internal casing pressure and temperature and controlling the annular pressure in the production stage was beneficial in ensuring the integrity of the cement sheath at the lower and upper parts of the packer, respectively. The research results provided an important reference for ensuring the integrity of the cement sheath of high-pressure gas wells.

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Section: Introductionmentioning

confidence: 99%

Experiment and failure mechanism of cement sheath integrity under development and production conditions based on a mechanical equivalent theory

Huang

et al. 2021

Energy Science & Engineering

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The Unconventional Unconventionals: Tectonically Influenced Regions, Stress States and Casing Failures

Casero¹,

Rylance²

2020

Day 3 Thu, February 06, 2020

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Not all unconventional plays are created equal, in a substantial number of regions around the world the tectonic environment is quite different from the typically relaxed and more passive states found widely in most, if not all, of the US unconventional plays. This is merely a function of the relative proximity of such plays to distinct geological features characterized by active tectonic plates and with dynamic margins and recent activity. The Nazca plate associated with the Andes, the Arabian plate linked with the Al-Hajar mountains and the Indian plate connected with the Himalayan mountain range are just a few examples of tectonically influenced regions, where potential hydrocarbon traps are subject to complex states of stress generated by convergent plates, subduction zones and associated faulting. This scenario often translates into severe strike-slip and reverse fault stress states. Additionally, the presence of both multi-layered and laminated formation geology as well as the presence of overpressure and pressure differentials, typical of tight gas and shale gas, can exacerbate this situation even further. This situation can result in an extremely challenging environment for the successful execution of hydraulic fracturing and the associated development of unconventional resources. This paper will demonstrate, that such complex stress-states will directly affect well completions and hydraulic fracturing in a multitude of ways, but that some of the most impactful consequences are often severe casing failures, production-liner restrictions and complex fracture initiation scenarios. Casing failures are responsible for increased intervention costs as well as higher costs for the upgraded and strengthened wells. Equally, such issues can severely impair efficient execution of the completion plan and create a bottle-neck to subsequent well production. Horizontal, complex and pancake fractures will typically develop in strike-slip / reverse fault stress states, often resulting in fracture conductivity and connectivity loss that will greatly impair the eventual well performance. Layer interface slippage and natural fault re-activation are dominant mechanisms for hydraulic fracture induced casing failures. Examples of micro-fracs, micro-seismic and other diagnostics will be presented aiming to document the practical difficulties encountered while completing wells in these complex environments. This paper will demonstrate that unconventional development in such environments requires a renewed focus on all aspects of well design and construction, from directional drilling and lateral placement to casing selection and lower completion design. All these considerations are made with the goal of enabling the competent delivery of a highly effective and conductive fracture network, to efficiently access and produce the hydrocarbon resource.

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Theoretical Analysis of the Micro Annulus of an Oil-Well Cement Sheath Formed via Cooling under Acid-Fracturing Conditions

et al. 2022

Processes

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The plastic deformation and interface micro annulus of oil-well cement during acid fracturing are key reasons for the failure of the wellbore seal and sustained casing pressure. However, most of the existing research ignores the influence of the wellbore cooling effect during acid fracturing, owing to which, the design conditions in the theoretical analysis may be inconsistent with those of the actual wellbore, and the calculation results may be biased. In this study, a novel elastoplastic mechanical model of the cement sheath was established. This model can analyze the yield state of the cement sheath under the influence of three-dimensional principal stress and consider the effect of the differential temperature stress on the interface debonding of the cement sheath from the beginning to the end of acid fracturing. Moreover, the generation mechanism and development law of the interface micro annulus were clarified. The findings indicated that the influence of the intermediate principal stress cannot be ignored; otherwise, the elastoplastic analysis results of the cement sheath may be conservative. During acid fracturing, the casing–cement sheath interface is influenced by the differential temperature stress, and the interface is debonded; however, a micro annulus is not generated. The debonding of the cement sheath–formation interface and micro annulus occurs only when the cement sheath is completely plastic. After acid fracturing, the interface micro annulus is likely to be generated at the casing–cement sheath interface, and the presence of the differential temperature stress may increase the formation risk of the interface micro annulus. The research results can provide theoretical guidance for the prediction of oil-well cement sheath interface seals under acid-fracturing conditions.

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Cementing Practices to Solve Well Integrity Challenges of Ultra Deep High Temperature Wells in Western China

Cited by 3 publications

References 14 publications

Experiment and failure mechanism of cement sheath integrity under development and production conditions based on a mechanical equivalent theory

Experiment and failure mechanism of cement sheath integrity under development and production conditions based on a mechanical equivalent theory

The Unconventional Unconventionals: Tectonically Influenced Regions, Stress States and Casing Failures

Theoretical Analysis of the Micro Annulus of an Oil-Well Cement Sheath Formed via Cooling under Acid-Fracturing Conditions

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