The hydraulic effects on torque and drag modelling have been thoroughly studied in the past, yet their interpretation still causes a lot of misunderstandings and confusions. Historical models disregard the circulation effects and focus on the fluid mass by employing buoyancy forces based on Archimedes principle. On the other hand, the reference model including the fluid circulation effects, introduced by R. F. Mitchell in the 1990s, consists in computing the forces due to internal and external fluids along the drill-string. The first type of models called Archimedes method directly produces an effective tension, while the second one generally called pressure area method produces a true tension that must be further transformed to get the effective tension. These different forms of tensions add even more confusion. By returning to the basic equations of the fluid effects on the drill string, an equivalency between Archimedes and pressure area models has been found for the case with no circulation. Furthermore, with the same principle, an Archimedes-like model is deduced for the case of fluid circulation, where the effects of fluid pressures, frictions, and flows could be more easily interpreted. These two hydraulic models, after implementation in a true stiff-string 3D model enable then to fairly compare the two approaches in terms of forces applied on the structure. The comparison of this Archimedes formulation with pressure area model gave sensibly the same results for various scenarios, proving the equivalency of the two approaches even with the case of circulating fluid. In addition to the model-to-model comparisons, torque and drag results are compared to field experiments at different depths. Flow rate was varied while reciprocating the drill string up and down, and the hook load was recorded for each flow rate and each tripping direction. The model-to-data comparisons showed a good agreement between the theoretical results and experimental data. An advanced Archimedes method with all fluid circulation effect has been developed. By tackling the problem of circulating fluid in the drill string using two different approaches and proving their equivalency, a better understanding of the hydraulic effects can be achieved, which in terms can help settle the possible debates and confusions that might arise by drilling engineers.
水力对扭矩和阻力建模的影响已经得到了深入的研究，但其解释仍然存在许多误解和混乱。历史模型忽略了循环效应，根据阿基米德原理利用浮力来关注流体质量。另一方面，R. F. Mitchell在20世纪90年代引入的包含流体循环效应的参考模型是计算沿钻柱的内外流体所产生的力。第一类模型称为阿基米德法，直接产生有效张力，而第二类模型通常称为压力区法，产生真张力，必须进一步转化才能得到有效张力。这些不同形式的紧张关系增加了更多的混乱。通过回归流体对钻柱影响的基本方程，在没有循环的情况下，阿基米德模型和压力面积模型之间存在等效性。此外，根据同样的原理，我们还推导出了流体循环的类似阿基米德的模型，在这种情况下，流体压力、摩擦和流动的影响可以更容易地解释。这两种水力模型在真正的硬管柱3D模型中实现后，可以比较两种方法在结构上施加的力。将阿基米德公式与压力面积模型进行比较，在各种情况下得出了大致相同的结果，证明了这两种方法即使在循环流体的情况下也是等效的。除了模型与模型之间的比较外，还将扭矩和阻力结果与不同深度的现场实验结果进行了比较。在上下往复钻柱时，改变流量，并记录每个流量和每个起下钻方向下的钩载荷。模型与数据的比较表明，理论结果与实验数据吻合较好。开发了一种先进的阿基米德方法，具有全流体循环效应。通过使用两种不同的方法来解决钻柱中循环流体的问题，并证明它们的等效性，可以更好地了解水力效应，从而有助于解决钻井工程师可能出现的争论和困惑。
{"title":"Fluid Circulation Effects on Torque and Drag Results, a New Take on an Old Subject","authors":"M. Mahjoub, N. Dao, M. Summersgill, S. Menand","doi":"10.2118/212558-ms","DOIUrl":"https://doi.org/10.2118/212558-ms","url":null,"abstract":"\u0000 The hydraulic effects on torque and drag modelling have been thoroughly studied in the past, yet their interpretation still causes a lot of misunderstandings and confusions. Historical models disregard the circulation effects and focus on the fluid mass by employing buoyancy forces based on Archimedes principle. On the other hand, the reference model including the fluid circulation effects, introduced by R. F. Mitchell in the 1990s, consists in computing the forces due to internal and external fluids along the drill-string. The first type of models called Archimedes method directly produces an effective tension, while the second one generally called pressure area method produces a true tension that must be further transformed to get the effective tension. These different forms of tensions add even more confusion.\u0000 By returning to the basic equations of the fluid effects on the drill string, an equivalency between Archimedes and pressure area models has been found for the case with no circulation. Furthermore, with the same principle, an Archimedes-like model is deduced for the case of fluid circulation, where the effects of fluid pressures, frictions, and flows could be more easily interpreted. These two hydraulic models, after implementation in a true stiff-string 3D model enable then to fairly compare the two approaches in terms of forces applied on the structure.\u0000 The comparison of this Archimedes formulation with pressure area model gave sensibly the same results for various scenarios, proving the equivalency of the two approaches even with the case of circulating fluid. In addition to the model-to-model comparisons, torque and drag results are compared to field experiments at different depths. Flow rate was varied while reciprocating the drill string up and down, and the hook load was recorded for each flow rate and each tripping direction. The model-to-data comparisons showed a good agreement between the theoretical results and experimental data.\u0000 An advanced Archimedes method with all fluid circulation effect has been developed. By tackling the problem of circulating fluid in the drill string using two different approaches and proving their equivalency, a better understanding of the hydraulic effects can be achieved, which in terms can help settle the possible debates and confusions that might arise by drilling engineers.","PeriodicalId":103776,"journal":{"name":"Day 2 Wed, March 08, 2023","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129570189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Khim Chhantyal, Å. Kyllingstad, Anders Hetland, Kjartan Thor Birgisson
A drill-off test is a special drilling test where the drawworks is locked and the string elasticity causes the bit to penetrate the formation at a decreasing weight on bit (WOB). It is often used as a tool for finding how the rate of penetration (ROP) varies as a function of WOB and for finding optimal drilling parameters. This paper sheds a critical light on the use of drill-off test by discussing various errors and pitfalls usually ignored today. The paper starts by presenting a simple but widely used method for converting surface hookload data into an ROP vs. WOB curve, commonly known as a drilling performance curve. Next, it discusses and tries to quantify various error sources, such as hookload sensor errors, residual wellbore drag, and formation inhomogeneities. The paper uses real field data and a comprehensive simulation model to illustrate the magnitude of the various errors and how they affect the drilling performance curve. Finally, the paper suggests ways to check the accuracy and validity of the drill-off tests. The analysis shows that the variable wellbore friction is an error source that depends on many parameters, such as string length, wellbore inclination, rotational string speed, and ROP. It also shows that it is possible to model the errors and apply correction formulas to improve the quality and accuracy of WOB and ROP. Although friction-related errors can be reduced by applying proper corrections to the estimated WOB and ROP, there is still a need to check the validity of the drill-off test results with other types of drilling tests. The paper presents several proposals for alternative and complementary drilling tests, such as drill-on test (here defined as a test where WOB is continuously increased), steady state (constant WOB) drilling test, combo test, and sinusoidal perturbations test.
{"title":"Drill-Off Tests for Drilling Optimization: Pitfalls and How to Avoid Them","authors":"Khim Chhantyal, Å. Kyllingstad, Anders Hetland, Kjartan Thor Birgisson","doi":"10.2118/212478-ms","DOIUrl":"https://doi.org/10.2118/212478-ms","url":null,"abstract":"\u0000 A drill-off test is a special drilling test where the drawworks is locked and the string elasticity causes the bit to penetrate the formation at a decreasing weight on bit (WOB). It is often used as a tool for finding how the rate of penetration (ROP) varies as a function of WOB and for finding optimal drilling parameters. This paper sheds a critical light on the use of drill-off test by discussing various errors and pitfalls usually ignored today. The paper starts by presenting a simple but widely used method for converting surface hookload data into an ROP vs. WOB curve, commonly known as a drilling performance curve. Next, it discusses and tries to quantify various error sources, such as hookload sensor errors, residual wellbore drag, and formation inhomogeneities. The paper uses real field data and a comprehensive simulation model to illustrate the magnitude of the various errors and how they affect the drilling performance curve. Finally, the paper suggests ways to check the accuracy and validity of the drill-off tests. The analysis shows that the variable wellbore friction is an error source that depends on many parameters, such as string length, wellbore inclination, rotational string speed, and ROP. It also shows that it is possible to model the errors and apply correction formulas to improve the quality and accuracy of WOB and ROP. Although friction-related errors can be reduced by applying proper corrections to the estimated WOB and ROP, there is still a need to check the validity of the drill-off test results with other types of drilling tests. The paper presents several proposals for alternative and complementary drilling tests, such as drill-on test (here defined as a test where WOB is continuously increased), steady state (constant WOB) drilling test, combo test, and sinusoidal perturbations test.","PeriodicalId":103776,"journal":{"name":"Day 2 Wed, March 08, 2023","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133255243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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