Wellbore Cleanness Under Total Losses in Horizontal Wells: The Field Study

2021 ◽  
Author(s):  
Alexey Ruzhnikov ◽  
Edgar Echevarria
Keyword(s):  
High Risk ◽  
Middle East ◽  
Field Study ◽  
Drilling Fluid ◽  
Horizontal Wells ◽  
Circulation Zone ◽  
Hole Cleaning ◽  
Lost Circulation ◽  
Cleaning Behavior

Abstract In the Middle East many of the matured fields have fractured or vugular formations where the drilling is continued without return to a surface. This situation has been commonly interpreted as lack of hole cleaning and high risk of stuck pipe. The manuscript describes a study performed to analyze the hole cleaning while blind drilling horizontal sections. Most of the losses while drilling across fractured or vugular formations happen sudden, and this represents a risk of formation instability and stuck pipe. Additionally, the cuttings accumulation may lead to a potential pack off. To understand the hole cleaning the annular pressure while drilling was introduced in different sections, what via change of the equivalent static and dynamic densities describes the cutting and cavings accumulation in the annulus. Additionally, the hole cleaning behavior with different fluids pumped through the drillstring (i.e. drilling fluid, water, water with sweeps) was studied. The proposed study was performed in 4 different fields, 9 wells, across horizontal 6⅛-in. sections with total lost circulation. It was identified that while drilling with full returns ECD vs ESD variations are within 1.5 ppg, those variations are matching with the modeling of hydraulics. Once total losses encountered the variations between ECD and ESD are very low - within 0.2 ppg - indicating that annular friction losses below the loss circulation zone are minimal. This support the theory that all the drilled cuttings are properly lifted from bottom and carried to the karst into the loss circulation zone and not fluctuating above the loss zone. Additionally, minor to no relation found in hole cleaning while drilling with mud or a water with sweeps. This finding also is aligned with the stuck pipe statistics that shows higher incidents of stuck pipe while drilling the with full circulation due to pack off. The manuscript confirms the theory of the hole cleaning in total lost circulation and application of different hole cleaning practices to improve it. The results of the study can be implemented in any project worldwide.

Study of the Cause of Lost Circulation while Drilling Fractured Carbonates

2021 ◽  
Author(s):  
Alexey Ruzhnikov
Keyword(s):  
Success Rate ◽  
Drilling Fluid ◽  
Circulation Zone ◽  
Lost Circulation ◽  
Carbonate Formation ◽  
New Information ◽  
Fractured Carbonate ◽  
Long Time ◽  
The Difference ◽  
Fractured Carbonates

Abstract Fractured carbonate formations are prone to lost circulation, which affects the well construction process and has longtime effect on well integrity. Depending on the nature of losses (either induced or related to local dissolutions) the success rate is different when the induced losses can be cured with a high chance, and the one related to dissolutions may take a long time, and despite multiple attempts, the success rate is normally low. To have a better understanding of the complete losses across the fractured carbonates, a series of studies were initiated. First, to understand the strength of the loss zone, the fracture closing pressure was evaluated studying the fluid level in the annulus and back-calculating the effect of drilling fluid density. Second, the formation properties across the loss circulation zones were studied using microresistivity images, dip data, and imaging of fluid-saturated porous media. The results of the studies brought a lot of new information and explained some previous mysteries. The formation strength across the lost circulation zone was measured, and it was confirmed that it remains constant despite other changes of the well construction parameters. Additionally, it was confirmed that the carbonates are naturally highly fractured, having over 900 fractures along the wellbore. The loss circulation zone was characterized, and it was confirmed that the losses are not related to the fractures but rather to the karst, dissolution, and megafractures. The size and dip of the fractures were identified, and it was proven the possibility to treat them with conventional materials. However, the size of identified megafractures and karst zones exceeding the fractures by 10 times in true vertical depth, and in horizontal wells the difference is even higher due to measured depth. This new information helps to explain the previous unsuccessful attempts with the conventional lost circulation materials. The manuscript provides new information on the fractured carbonate formation characterization not available previously in the literature. It allows to align the subsurface and drilling visions regarding the nature of the losses and further develop the curing mechanisms.

Factorial Design Validation of an Environmentally Benign Water-Based Drilling Fluid from Sweet Potato Peels at Elevated Temperatures

2021 ◽  
Author(s):  
Ifeanyichukwu Ebuzeme ◽  
Oladipo Olatunji ◽  
Babatope Olufemi
Keyword(s):  
Factorial Design ◽  
Sweet Potato ◽  
Yield Point ◽  
Elevated Temperatures ◽  
Drilling Fluid ◽  
Plastic Viscosity ◽  
Environmentally Benign ◽  
Hole Cleaning ◽  
Lost Circulation ◽  
Potato Peels

Abstract In recent years, several research types have been carried out to produce environmentally-benign drilling fluid additives using locally sourced substances. Still, the formulation of a more effective and cheaper viscosifier for a better hole cleaning ability that lowers risk in lost circulation zones, especially at higher temperatures, remains a critical research subject. This study examines the use of Sweet Potato Peels Extract (PPE), a more readily available by-product, as a drilling fluid additive. A 23 factorial experiment that considers temperature, PPE and Xanthan Gum (X.G.) as factor variables and viscosity as a response variable was conducted for field optimisation. In this research, the PPE and other commercial polymers were measured at different concentrations and combined in a specified ratio of 1:1 by mass to verify the levels of interaction between the additives on the mud weight, yield point (Y.P.), and plastic viscosity (P.V.) of the formulated drilling mud. The additives’ effects were then recorded using a mud balance, a viscometer, and a heater for temperature variance. The results were then compared with the control mud to ascertain the additives’ effectiveness. Experimental results revealed that the PPE and X.G. increased the Y.P. and P.V. at 104 °F and 176 °F, respectively. On adding 6 g of X.G. to the control mud (8.97 ppg), at 104 °F and 176 °F, the Y.P. increased by 88% and 11%, respectively, and the 3 g PPE + 3 g X.G. gave a better inference at 104 °F and 176 °F with a 92% and 38% increase respectively. This increase is a result of higher potassium content in the PPE from chemical laboratory analysis. Apart from the optimum ratio by mass of 1:1 above, the combination effects or results are shown using the factorial design experiment. The factor variables were modelled into a mathematical equation that indicates PPE additive as the most significant parameter on the yield point. The second component of viscosity, plastic viscosity (P.V.), followed a similar trend. Furthermore, PPE and X.G.'s effect on plastic viscosity at 176 °F decreased slightly with an increase in the control mud's salinity. This novel combination offers a more cost-effective and better-performing viscosifier than the conventional X.G. from the above results. The model helps predict downhole conditions better as it shows the interactive effects of the various additives and can help inform decisions at the surface. A better hole cleaning ability, lower risk in lost circulation zones, and reduced Non-Productive Time would be the benefits of using this formulation.

scholarly journals A Chemical Lost Circulation Agent for Severe Leakage in Drilling

2013 ◽  
Vol 6 (1) ◽  
pp. 48-54 ◽  
Author(s):  
Kaihe Lv ◽  
Hanyi Zhong ◽  
Guanlong Ren
Keyword(s):  
Particle Size ◽  
Compressive Strength ◽  
Significant Influence ◽  
Drilling Fluid ◽  
Drilling Process ◽  
Circulation Zone ◽  
Reaction Products ◽  
Lost Circulation ◽  
Granular Solid ◽  
Reaction With Water

This study presents a chemical lost circulation agent with some distinct advantages that make it suitable for use in controlling severe leakage during drilling process. It is a granular solid with irregular shape and able to bridge or fill the cracks and other porous or faulty formations into where the drilling fluid is lost. Then this agent will undergo a chemical reaction with water, and the reaction products fill between particles and bind tightly lost circulation agent particles to each others or to the rocks at the lost circulation zone, thus effectively enhance the compressive strength of the cementing body formed by the agent and prevent lost circulation. Temperature, particle size, and additives added have been shown to have a significant influence on the consolidating rate and compressive strength of the cementing body. In addition, the cementing body has certain permeability, and the permeability can be adjusted, so this agent is proper for use to control lost circulation in reservoir.

Quantification of the Loss Conduit Aperture During Lost Circulation in Fractured Carbonates

2021 ◽  
Author(s):  
Alexey Ruzhnikov ◽  
Ashley Johnson
Keyword(s):  
Drilling Fluid ◽  
Rock Properties ◽  
Circulation Zone ◽  
Lost Circulation ◽  
New Information ◽  
Fractured Carbonate ◽  
The Difference ◽  
New Vision ◽  
Carbonate Formations ◽  
Fractured Carbonates

Abstract Fractured carbonate formations around the world are prone to lost circulation that not only affects the well construction process but creating a longtime effect on the wellbore integrity. Despite multiple attempts to cure them the success rate is usually low. This manuscript is aiming to provide a new vision on the reason of lost circulation across carbonates. To have better understanding of the complete losses across the fractured carbonates the series of studies were initiated. At first to understand the strength of the loss zone the fracture closing pressure was evaluated via study of the fluid level in the annulus and back-calculation of the drilling fluid density effect on it. Secondary, the rock properties across the loss circulation zones were studied by using the microresistivity images, dip data, and imaging of fluid-saturated porous media. At last, the trial tests with different treatment materials were performed to evaluate the effect of it on curing the losses. The results of the studies brought new information and explained some previous unknowns. The formation strength across lost circulation zone was measured and it was confirmed to remain constant despite other changes of the well conduction parameters. It was also confirmed that the carbonates are naturally highly fractured having over 900 fractures along the wellbore. The lost circulation zone was characterized, and it was confirmed that the losses were not related to the fractures but rather to the karst, dissolution and to mega-fractures. The size and dip of the fractures were identified, and it was proven the possibility to treat them with conventional materials. However, the size of identified mega-fractures and karst zones exceed the fractures by 100 times in true vertical depth, and in horizontal wells the difference is thousands times due to measured depth. This new information explains the previous unsuccessful attempts with the conventional lost circulation materials. Further based on the newly available information the mathematic description of the lost circulation zones was provided.

Whose risk? Bank de-risking and the politics of interpretation and vulnerability in the Middle East and North Africa

2021 ◽  
pp. 1-16
Author(s):  
Sherine El Taraboulsi-McCarthy
Keyword(s):  
Political Economy ◽  
High Risk ◽  
Middle East ◽  
Money Laundering ◽  
North Africa ◽  
Civil Society Organizations ◽  
Negative Consequences ◽  
Local Authorities ◽  
The Impact ◽  
Politics Of Interpretation

Abstract Following the events of 11 September 2001, measures aimed at countering the financing of terrorism (CFT) were intensified by States. Many countries around the world adopted strict anti-money laundering and CFT regulations for the transfer of funds globally. This process increased the costs of complying with regulatory requirements and imposed high penalties on banks for non-compliance. As a result, preventive measures – often known as “de-risking” – were taken up by banks, including terminating the accounts of clients perceived as “high-risk” for money laundering or terrorist financing, and delaying transfers. These measures, however, have had negative consequences, reducing financial access for local civil society organizations in conflict-affected contexts that are deemed high-risk for terrorist activities. Drawing on five years of research to understand the impact of de-risking on conflict-affected contexts from a local perspective, this paper reflects on the local political economy of CFT, with a focus on the Middle East and North Africa. It explores two key areas of inquiry. The first of these is the politics of interpretation – how counterterrorism as a discourse and a set of practices, of which CFT is one, gets interpreted by local authorities and banks, and subsequently gets reinterpreted to the population. This also has implications for which local actors are better positioned to access funds than others, and why. The second area of inquiry is the politics of vulnerability – how the local political economy impact of CFT can increase the social and economic vulnerabilities of some groups more than others. This paper demonstrates that under the guise of “counterterrorism”, local authorities in conflict-affected contexts have used CFT to restrict the non-profit and philanthropic space and are using banking regulations to shape that space in ways that are bound to have negative medium- and long-term implications for it.

Machine-Learning for the Prediction of Lost Circulation Events - Time Series Analysis and Model Evaluation

2021 ◽  
Author(s):  
Arturo Magana-Mora ◽  
Mohammad AlJubran ◽  
Jothibasu Ramasamy ◽  
Mohammed AlBassam ◽  
Chinthaka Gooneratne ◽  
...  
Keyword(s):  
Machine Learning ◽  
Time Series ◽  
Real Time ◽  
Large Scale ◽  
Model Comparison ◽  
Drilling Fluid ◽  
Sensor Data ◽  
False Alarms ◽  
Suitable Model ◽  
Lost Circulation

Abstract Objective/Scope. Lost circulation events (LCEs) are among the top causes for drilling nonproductive time (NPT). The presence of natural fractures and vugular formations causes loss of drilling fluid circulation. Drilling depleted zones with incorrect mud weights can also lead to drilling induced losses. LCEs can also develop into additional drilling hazards, such as stuck pipe incidents, kicks, and blowouts. An LCE is traditionally diagnosed only when there is a reduction in mud volume in mud pits in the case of moderate losses or reduction of mud column in the annulus in total losses. Using machine learning (ML) for predicting the presence of a loss zone and the estimation of fracture parameters ahead is very beneficial as it can immediately alert the drilling crew in order for them to take the required actions to mitigate or cure LCEs. Methods, Procedures, Process. Although different computational methods have been proposed for the prediction of LCEs, there is a need to further improve the models and reduce the number of false alarms. Robust and generalizable ML models require a sufficiently large amount of data that captures the different parameters and scenarios representing an LCE. For this, we derived a framework that automatically searches through historical data, locates LCEs, and extracts the surface drilling and rheology parameters surrounding such events. Results, Observations, and Conclusions. We derived different ML models utilizing various algorithms and evaluated them using the data-split technique at the level of wells to find the most suitable model for the prediction of an LCE. From the model comparison, random forest classifier achieved the best results and successfully predicted LCEs before they occurred. The developed LCE model is designed to be implemented in the real-time drilling portal as an aid to the drilling engineers and the rig crew to minimize or avoid NPT. Novel/Additive Information. The main contribution of this study is the analysis of real-time surface drilling parameters and sensor data to predict an LCE from a statistically representative number of wells. The large-scale analysis of several wells that appropriately describe the different conditions before an LCE is critical for avoiding model undertraining or lack of model generalization. Finally, we formulated the prediction of LCEs as a time-series problem and considered parameter trends to accurately determine the early signs of LCEs.

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