Drilling the Un Drillable: A Case Study of the Bela Well in Makran Accretionary Prism

2021 ◽  
Author(s):  
Umair Ahmed Baig ◽  
Ghulam Nabi Agha
Keyword(s):  
Pore Pressure ◽  
Accretionary Prism ◽  
Well Being ◽  
Lessons Learned ◽  
Planning Stage ◽  
Lost Circulation ◽  
Hole Pressure ◽  
Bottom Hole Pressure ◽  
Fracture Pressure ◽  
Bottom Hole

Abstract The Bela Well is situated on Makran accretionary prism with several active mud volcanoes that makes conventional drilling challenging due to the extremely high pore pressure i.e. in excess of 15,000 psi and a very narrow window between pore pressure and fracture pressure. This adverse condition was observed in the 9 offset wells drilled within this basin with problems related to wellbore instability, lost-circulation zones and over-pressured formations leading to kick/loss well control scenarios that resulted in the well being abandoned prior to reaching the geological target. The constraint to drill the planned and 8-3/8" section in the well was the unpredictability of the pore/fracture pressure in the Panjgur formation representing a high-level operational risk. Solutions to tackle such a high pressure well included incorporating heavy grade casing i.e. 9-7/8"- 72 ppf in the planning stage, utilization of a 3000 HP rig to cater to extreme axial and hydraulic loads. Whereas MPD was planned as a technique to cater to the narrow window between pore pressure and fracture pressure. A managed pressure drilling (MPD) system was utilized to enable drilling the 8-3/8" hole section. An MPD system that applies constant bottom hole pressure enabled drilling the section with statically underbalanced mud weight by keeping a constant surface back pressure to prevent any influx. The drilling window for MPD was validated by determining the Bottom Hole Pressure where both, an influx from the formation and fluid losses occurred. These values were later used to establish the target Equivalent Circulating Density-ECD to drill the hole accordingly. Trips for BHA change or BOP test were performed by placing a pressurized mud cap in the wellbore. This paper describes in detail the successful MPD application resulted in the first well being drilled in the Makran accretionary prism to a depth of 5000 m. Lessons learned and challenges encountered will also be discussed in this paper

Bottom Hole Pressure Management in a Highly Permeable and Narrow Margin MPD Operation

2016 ◽  
Author(s):  
Ugochukwu Oseme ◽  
Sunday Awe ◽  
Obinna Amah ◽  
Adeyemi Erinle ◽  
Ayodele Akinfolarin ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Niger Delta ◽  
Success Factor ◽  
Hole Pressure ◽  
Bottom Hole Pressure ◽  
Critical Success ◽  
Fracture Pressure ◽  
Bottom Hole ◽  
Reservoir Permeability ◽  
Fracture Gradient

ABSTRACT Application of Managed pressure drilling (MPD) technology with other techniques to maintain constant Bottom Hole pressure (BHP) has been found to enhance drilling operations in applications where the margin between the pore pressure and fracture gradient is narrow and the reservoir permeability is high. Classic examples of such applications are deep water drilling, high pressure and high temperature (HPHT) regime and depleted reservoir environments. In the Niger Delta, HPHT reservoirs can be found in well depths up to 17000 ftss with a drilling window range of 0.4 to1.6ppg. Typical reservoir characteristics are formation permeability of 124 – 204mD and reservoir mobility of 112 – 1000mD/cp. Generally in this type of environment and essentially where there are high uncertainties in the reservoir pressures and formation characteristics, significant process safety incidents have been found to occur during pumps off events as a result of variations in BHP outside the allowable limits of pore pressure (lower limit) and fracture gradient (upper limit). The risks of exceeding the allowable limits are the possibility of taking significant influx volume if BHP falls below the pore pressure and loss of well bore integrity if the BHP exceeds the fracture pressure. Consequences of any of these events are high nonproductive time (NPT), well cost escalation and inability to achieve well objectives. This paper illustrates how in the recent HPHT exploration campaign carried out in Niger Delta, managing BHP was identified as a critical success factor. Hydrocarbon reserves of the exploratory objectives were successfully and safely unlocked by using MPD to maintain BHP within the allowable limits. The paper also illustrates how MPD application was enhanced by the use of high resolution pressure while drilling (PWD) technology.

First MPD Project in Myanmar Successfully Completed on Deepwater Exploration Well

2021 ◽  
Author(s):  
Harpreet Kaur Dalgit Singh ◽  
Bao Ta Quoc ◽  
Benny Benny ◽  
Ching Shearn Ho
Keyword(s):  
Pore Pressure ◽  
Control Device ◽  
Back Pressure ◽  
Deepwater Drilling ◽  
Hole Pressure ◽  
Bottom Hole Pressure ◽  
Bottom Hole ◽  
Managed Pressure Drilling ◽  
Pore Pressure Prediction ◽  
Exploration Well

Abstract With the many challenges associated with Deepwater Drilling, Managed Pressure Drilling has proven to be a very useful tool to mitigate many hurdles. Client approached Managed Pressure Drilling technology to drill Myanmar's first MPD well on a Deepwater exploration well. The well was drilled with a Below Tension Ring-Slim Rotating Control Device (BTR-S RCD) and Automated MPD Choke System installed on semi-submersible rig, Noble Clyde Boudreaux (NCB). The paper will detail MPD objectives, application and well challenges, in conjunction with pore pressure prediction to manage the bottom hole pressure to drill to well total depth safely and efficiently. This exploration well was drilled from a water depth of 590m from a Semisubmersible rig required MPD application for its exploratory drilling due to uncertainties of drilling window which contained a sharp pressure ramp, with a history of well bore ballooning there was high potential to encounter gas in the riser. The Deepwater MPD package integrated with the rig system, offered a safer approach to overcome the challenges by enhanced influx monitoring and applying surface back pressure (SBP) to adjust bottom hole pressures as required. Additionally, modified pore pressure hunting method was incorporated to the drilling operation to allow more accurate pore pressure prediction, which was then applied to determine the required SBP in order to maintain the desired minimum overbalance while drilling ahead. The closed loop MPD circulating system allowed to divert returns from the well, through MPD flow spool into MPD distribution manifold and MPD automated choke manifold system to the shakers and rig mud gas separator (MGS). The automated MPD system allows control and adjustments of surface back pressure to control bottom hole pressure. MPD technology was applied with minimal overbalance on drilling and connections while monitoring on background gases. A refined pore pressure hunting method was introduced with manipulation of applied surface back pressure to define this exploration well pore pressure and drilling window. The applied MPD Deepwater technique proved for cost efficiency and rig days to allow two deeper casing setting depths and eliminating requirement to run contingency liners. MPD system and equipment is proving to be a requirement for Deepwater drilling for optimizing drilling efficiency. This paper will also capture detailed lesson learned from the operations as part of continuous learning for improvement on Deepwater MPD drilling.

The Theory and the Practical Validation of the Fluid Level Position in the Annulus During Lost Circulation

2021 ◽  
Author(s):  
Alexey Ruzhnikov ◽  
Edgar Echevarria
Keyword(s):  
Flow Rate ◽  
Drilling Fluid ◽  
Time Interval ◽  
Fluid Level ◽  
Drilling Tool ◽  
Lost Circulation ◽  
Hole Pressure ◽  
Bottom Hole Pressure ◽  
Bottom Hole ◽  
Carbonate Formations

Abstract Carbonate formations around the world and specifically in a Middle East are prone to have total losses while drilling. And the nature of the losses often related to the highly fractured formations of the pay zone. When such fracture(s) is crossed by the wellbore the lost circulation initiated and led to a drilling without a return to a surface. To avoid undesired well control event or wellbore instability and to maintain the constant bottom hole pressure the mud cap drilling strategy often used as a preventative measure. The mud cap can be either the continuous or based on some volume or time interval, depends on the local practices or the policy of an operator. The mud cap flow rate as well as mud cap mud weight are often based on the best practices, not supported by an engineering study. To understand the behavior of the drilling fluid level in the annulus while drilling with total losses the drilling bottom hole assembly equipped with annular pressure while drilling tool was used. As the drilling required to use the continuous mud cap, then the specific guideline was developed on measurement of the bottom hole pressure and further conversion of it to the fluid level. The study was performed across pay zone with one or several loss circulation zones identified. As the result it was confirmed that the used mud cap flow rate had minor to none effect on the fluid level position in the annulus and that the bottom hole pressure remained the same. It showed as well that different loss zones are behaving in a different way, what can be considered as a factor affecting their ability to be sealed. The obtained knowledge and the information should help to understand better the loss circulation behavior as well be an important step toward development of the product which may cure the losses in high fractured carbonate formations. The results of the study can be implemented in any other project or a field.

Fully Automatic Managed Pressure Drilling Technology, The Answer to Weeks of Well Complications Including High Temp, Narrow Mud Window & CO2 Influx in Challenging Exploration Wells

2021 ◽  
Author(s):  
Muhammad Jamaluddin Muhammad ◽  
Carlos Iturrios ◽  
Abdallah Kadadha ◽  
Mojtaba Alqatari ◽  
Ayoub Hadj-Moussa
Keyword(s):  
Pore Pressure ◽  
Drilling Process ◽  
Formation Pressure ◽  
Hole Pressure ◽  
Bottom Hole Pressure ◽  
Bottom Hole ◽  
Managed Pressure Drilling ◽  
Fully Automatic ◽  
Gain Loss

Abstract Managed Pressure Drilling is an adaptive drilling technique used to precisely assess the formation pressure limits and manage the annular pressure profile accordingly. MPD uses a lighter mud density that with assistance of surface backpressure maintain the overbalance condition, and the dynamic adjustment of this surface pressure allows to maintain Constant Bottomhole Pressure (CBHP) in both dynamic and static conditions. Generally, MPD system reduces the extra overbalanced pressure applied on a formation while drilling conventionally Recently, the operator utilized Managed Pressure Drilling (MPD) Constant bottom hole pressure (CBHP) technique to drill a challenging HPHT gas well successfully through an exploration field. The case study field elaborates challenges of uncertain formation pressure, narrow pore pressure-fracture pressure window and high background gas readings leading to extreme well complications. These challenges were counteracted with the implementation of Managed pressure drilling MPD technology, enabling to drill a well without any complications. To coupe with the complications including high temperature, narrow mud window & CO2 influx, MPD technology was called to be utilized in the challenging exploration field. With the implementation of MPD in this exploration drilling campaign, the case study well proved to optimize the overall drilling process, hence proving an answer to the previous problems in the field. The subject well was the first well to reach this depth. As a starting point, the actual bottom hole pressure limitations were established by performing MPD pore pressure tests, due to the lack of data as the only other option was to rely on geo-mechanics interpretations which is not very accurate, considering the case study specifically. Being it an exploration field, the bottom hole conditions were inconsistent and uncertain. The fully automatic MPD system enabled real-time evaluation and instant adjustment of the bottom-hole formation pressure changes, throughout the drilling process. The precise and instant control of bottom-hole pressure was the key factor of the overall success, hence mitigating any well complications, which previously costed weeks of rig days and associated oil based mud costs during losses. Since MPD technique evaluates & optimizes the required mud weight, hence saving the unnecessary overbalance on the well which had been the cause of several problems previously like losses, differential sticking and ballooning. Furthermore, for these critical narrow window wells, there was a need of a fool proof gain/loss monitoring system to stay top of the game all times. The sophisticated early kick/loss detection feature of the MPD system added value to the operation, which was independent of the conventional rig mud pit transfers and mixing which usually trigger false gain/loss alarms. The narrow drilling window was exacerbated by the increase in annulus frictional losses for these extended wells. The approach of ‘Prevention is always better than cure’ was adopted by the operator, since MPD prevents/mitigates a lot of hazards before they happen. This publication summarizes the details of how the MPD CBHP technique, early kick detection system & instant control system made it possible to efficiently and successfully execute the drilling process safely. It was proved that real time monitoring, and instant reactions are necessary to be able to adjust the BHP to keep the well under control throughout the drilling and post drilling operations like reaming trip in these types of high gas bearing formations. Hence MPD enabled the drilling of complex geological and weak fracture strength formations without any NPT for well control situations with the few value-added benefits like improved ROP, extending the total depth by 1300 ft additional to the initial plan achieving the deepest TVD (true vertical depth) drilled in the field.

scholarly journals Production behavior evaluation on multilayer commingled stress-sensitive carbonate gas reservoir

2020 ◽  
pp. 014459872096415
Author(s):  
Jianlin Guo ◽  
Fankun Meng ◽  
Ailin Jia ◽  
Shuo Dong ◽  
Haijun Yan ◽  
...  
Keyword(s):  
Early Stage ◽  
Sedimentary Environment ◽  
Production Performance ◽  
Total Production ◽  
Inversion Algorithm ◽  
Gas Reservoir ◽  
Hole Pressure ◽  
Bottom Hole Pressure ◽  
Bottom Hole ◽  
Production Behavior

Influenced by the complex sedimentary environment, a well always penetrates multiple layers with different properties, which leads to the difficulty of analyzing the production behavior for each layer. Therefore, in this paper, a semi-analytical model to evaluate the production performance of each layer in a stress-sensitive multilayer carbonated gas reservoir is proposed. The flow of fluids in layers composed of matrix, fractures, and vugs can be described by triple-porosity/single permeability model, and the other layers could be characterized by single porosity media. The stress-sensitive exponents for different layers are determined by laboratory experiments and curve fitting, which are considered in pseudo-pressure and pseudo-time factor. Laplace transformation, Duhamel convolution, Stehfest inversion algorithm are used to solve the proposed model. Through the comparison with the classical solution, and the matching with real bottom-hole pressure data, the accuracy of the presented model is verified. A synthetic case which has two layers, where the first one is tight and the second one is full of fractures and vugs, is utilized to study the effects of stress-sensitive exponents, skin factors, formation radius and permeability for these two layers on production performance. The results demonstrate that the initial well production is mainly derived from high permeable layer, which causes that with the rise of formation permeability and radius, and the decrease of stress-sensitive exponents and skin factors, in the early stage, the bottom-hole pressure and the second layer production rate will increase. While the first layer contributes a lot to the total production in the later period, the well bottom-hole pressure is more influenced by the variation of formation and well condition parameters at the later stage. Compared with the second layer, the scales of formation permeability and skin factor for first layer have significant impacts on production behaviors.

Study of the process of changing of the bottom hole pressure in time under the conditions of gaslift flowing

2020 ◽  
Author(s):  
M. Mokliak ◽  
B. Mishchuk ◽  
A. Hrytsanchuk ◽  
M. Schepanskyi
Keyword(s):  
Hole Pressure ◽  
Bottom Hole Pressure ◽  
Bottom Hole

Successful Application of Managed Pressure Drilling MPD Technology to Reach TD in a Narrow Margin HPHT Well in the North Sea – A Case History

2021 ◽  
Author(s):  
Babar Kamal ◽  
Emil Stoian ◽  
Graeme MacFarlane
Keyword(s):  
Pore Pressure ◽  
North Sea ◽  
Back Pressure ◽  
Lessons Learned ◽  
The North ◽  
Pull Out ◽  
Bottom Hole ◽  
Managed Pressure Drilling ◽  
Integrity Tests ◽  
Remedial Work

Abstract This paper reviews the recently concluded successful application of a Managed Pressure Drilling (MPD) system on a High-Pressure High-Temperature (HPHT) well with Narrow Mud Weight Window (NMWW) in the UK sector in the Central North Sea. Well-A was drilled with the Constant Bottom Hole Pressure (CBHP) version of MPD with a mud weight statically underbalanced and dynamically close to formation pore pressure. Whilst drilling the 12-1/2" section of the well with statically under-balanced mud weight, to minimize the overbalance across the open hole, an influx was detected by the MPD system as a result of drilling into a pressure ramp. The MPD system allowed surface back pressure to be applied and the primary barrier of the well re-established, resulting in a minimal influx volume of 0.06 m3 and the ability to circulate the influx out by keeping the Stand Pipe Pressure (SPP) constant while adjusting Surface Back Pressure (SBP) through the MPD chokes in less than 4 hours with a single circulation. After reaching the 12-1/2" section TD, only ~0.025sg (175 psi) Equivalent Mud Weight (EMW) window was available to displace the well and pull out of hole (POOH) the bottom hole assembly (BHA) therefore, 3 × LCM pills of different concentrations were pumped and squeezed into the formation with SBP to enhance the NMWW to 0.035sg EMW (245 psi) deemed necessary to kill the well and retrieve BHA. MPD allowed efficient cement squeeze operations to be performed in order to cement the fractured/weak zones which sufficiently strengthened the well bore to continue drilling. A series of Dynamic Pore Pressure and Formation Integrity Tests (DPPT and DFIT) were performed to evaluate the formation strength post remedial work and to define the updated MMW. Despite the challenges, the MPD system enabled the delivery of a conventionally un-drillable well to target depth (TD) without any unplanned increase/decrease in mud weight or any costly contingency architecture operations, whilst decreasing the amount of NPT (Non Productive Time) and ILT (Invisible Lost Time) incurred. This paper discusses the planning, design, and execution of MPD operations on the Infill Well-A, the results achieved, and lessons learned that recommend using the technology both as an enabler and performance enhancer.

scholarly journals A Unified Formula for Determination of Wellhead Pressure and Bottom-hole Pressure

2013 ◽  
Vol 37 ◽  
pp. 3291-3298 ◽  
Author(s):  
Mingze Liu ◽  
Bing Bai ◽  
Xiaochun Li
Keyword(s):  
Wellhead Pressure ◽  
Hole Pressure ◽  
Bottom Hole Pressure ◽  
Bottom Hole
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