Quantitative Analysis of Mud Losses in Naturally Fractured Reservoirs: The Effect of Rheology

Majidi, Reza; Miska, Stefan; Thompson, L.G.; Yu, Mengjiao; Jian-guo, Zhang

doi:10.2118/114130-pa

Cited by 62 publications

(30 citation statements)

References 7 publications

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“…Recognizing the essential role of the fluid rheology, Majidi et al 6 developed a theoretical model for a more realistic and frequently used rheological behavior of drilling fluids; i.e., Yield-Power-Law (YPL) fluids 7 . The mathematical model for Yield-Power-Law fluids was derived using a similar approach involved with Lietard's model.…”

Section: Introductionmentioning

confidence: 99%

“…However, in this model 6 , the formation fluid was not accounted for since it was assumed that the whole overbalance pressure was applied only across drilling fluid bank and no pressure profile was considered beyond the front of the invading mud in the fracture. This means that no resistance was considered against invading mud due to the infinite compressibility or low viscosity of formation fluids.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of Drilling Fluid Losses in Naturally Fractured Formations

Majidi

Miska

et al. 2008

All Days

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Significant mud losses often occur while drilling in fractured formations. Severe problems arise when drilling fluids invade high permeability conductive fractures that the well path intercepts. The industry has recently started to monitor mud loses in order to identify the fractures and characterize them. Methodologies are available to characterize the geometry and conductivity of the fractures by quantitative analysis of field measurements. These methodologies are mainly based on mathematical models that describe the physical phenomenon and the mechanism under which the flow within the fractures takes place. Once the models are provided one can look for causes of the problem and methods to minimize it.This paper presents a new model for mud loss of non-Newtonian drilling fluids into naturally fractured formations. Flow of Yield-Power-Law (Herschel-Bulkley) fluids has been coupled with Newtonian reservoir fluid in a single fracture. The governing equations are derived based on principles of conservation of mass and linear momentum for drilling fluid and pressure diffusion for reservoir fluid. Results are obtained based on semi-numerical solutions and plotted in terms of mud loss volumes versus time. The results demonstrate how rheology of the drilling fluid and formation fluid properties can influence mud losses. The relative contributions of both drilling and reservoir fluids is determined and compared.This model allows for predicting fluid losses for a given drilling fluid, formation fluid and operational conditions. Conversely, one can evaluate hydraulic aperture of the fractures by continuously monitoring mud losses and finding the best fit of field measurements of mud loss to the model. Field data are used to demonstrate the practical application of the proposed technique.The proposed model is valuable for drilling operations because it can help in minimizing the loss of expensive drilling fluids through optimization of drilling fluid rheological properties and selecting appropriate lost circulation materials. The model also benefits production operations by minimizing formation damage. In addition, well completion schemes can be optimized based on the improved knowledge of the near-wellbore fracture characteristics.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling of Drilling Fluid Losses in Naturally Fractured Formations

Majidi

Miska

et al. 2008

All Days

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“…Accordingly, Eq. 5 can be simplified using the formulation proposed by Majidi et al 2010.As an example, the data shown in Table 1 is used to calculate the fluid loss volume. The volume of loss for a fracture with 500 microns width is shown in Fig.…”

Section: Losses Through Small Natural Fracturesmentioning

confidence: 99%

Integrated Workflow for Lost Circulation Prediction

Ghalambor

Salehi

Shahri

et al. 2014

Day 2 Thu, February 27, 2014

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Lost circulation has plagued the industry since the beginning of drilling. Historically, severity of losses has been categorized based on the amount of barrels lost to the formation, i.e., seepage, partial, and total. Though helpful, this strategy doesn't help understand the underlying drive mechanism(s) for losses and doesn't provide enough data to propose a solution. The recently adopted category is focused on the lost-circulation mechanism based on the properties of the exposed formation; these classifications are losses to 1) pore throats, 2) induced or natural fractures, and 3) vugs or caverns. This study provides an integrated workflow to predict expected losses for such classification/mechanism of losses. Mud loss through fracturing is categorized based on fracture types, i.e., natural or induced fractures. Different models are used with respect to the fluid-loss mechanism in natural and induced fractures. These models take into account the effect of fracture breathing. In addition, mud loss through the pores on the wellbore and the fracture face is modeled based on formation and mud-cake filtration properties, coupled with the fracture losses. Losses through induced fractures generally occur when ECD exceeds fracture gradient. This happens due to erroneous prediction of the mud weight window, lack of the key information, harsh downhole pressure/temperature and some other operational factors. A field case from deep water Gulf of Mexico is presented in this paper showing how an inaccurate mud window can yield in drastic mud losses. In addition, rock properties and field in-situ stress govern fracture width and fracture propagation. Losses to vugs/caverns are usually total losses due to very large openings in the rock; recommendations are provided on how to control severe losses. Lost circulation not only causes the adverse effect of mud loss itself; it can also lead to several other issues, such as formation damage, stuck pipe, hole collapse, and well-control incidents. The current industry trend is moving towards drilling more low-pressure zones, and lost-circulation planning is becoming a vital part of these projects. Knowledge of the type and the expected amount of mud loss can help engineers select the most appropriate and effective solution and preplan accordingly. This information also provides criteria to evaluate the effectiveness of the applied lostcirculation strategy. In this study we review LCM treatments, wellbore strengthening, MPD, and CwD as some of the most common remedial techniques.

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“…They believed that the mud losses would eventually stop because of the yield stress of drilling fluid. Majidi et al presented a mathematical model for Herschel‐Bulkley drilling‐fluid losses in naturally fractured formations, the effect of mud rheological properties was investigated, and it was found that yield stress can control the ultimate volume of losses, and the shear‐thinning effect can greatly decrease the rate of losses.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of gas‐liquid displacement between borehole and gassy fracture using response surface methodology

Tang

Chen

et al. 2019

Energy Science & Engineering

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Gas‐liquid displacement occurs often in fractured gas reservoirs, and can cause gas kick and mud leakage, resulting in a very high risk of losing well control. To analyze gas‐liquid displacement between borehole and gassy fracture, we used computational fluid dynamics to simulate its behaviors. We also used response surface methodology (RSM) to design numerical experiments. The effects of fracture width, bottom‐hole differential pressure, mud density, mud viscosity, and mud displacement were taken into account. We used RSM to determine the influence of the multifactor interaction of gas‐liquid displacement and established an empirical formula for the gas displacement rate. The results show that gas‐liquid displacement is proportional to fracture width, bottom‐hole differential pressure, mud density, and mud displacement; however, the displacement is inversely proportional to mud viscosity. The sensitivity sequence of the gas‐liquid displacement rate is fracture width > bottom‐hole differential pressure > mud viscosity > mud density > mud velocity. The impact of fracture width is clearly higher than that of the other factors, while the mud velocity has almost no impact. Our established empirical formula can be used to predict bottom‐hole gas kick and drilling mud leakage and to inversely predict the fracture width and formation gas pressure.

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Quantitative Analysis of Mud Losses in Naturally Fractured Reservoirs: The Effect of Rheology

Cited by 62 publications

References 7 publications

Modeling of Drilling Fluid Losses in Naturally Fractured Formations

Modeling of Drilling Fluid Losses in Naturally Fractured Formations

Integrated Workflow for Lost Circulation Prediction

Numerical investigation of gas‐liquid displacement between borehole and gassy fracture using response surface methodology

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