Reclaiming the Operating Window: A Managed Pressure Cementing Workflow to Achieve Zonal Isolation Success in a Mature Field

2021 ◽  
Author(s):  
Jeffrey Smith ◽  
Lucas Rossi ◽  
Christopher Mehler ◽  
Jon Todd Eberhardt ◽  
Christopher Scarborough ◽  
...  
Keyword(s):  
Best Practices ◽  
Pore Pressure ◽  
Stability Control ◽  
Wellbore Stability ◽  
Optimized Design ◽  
Additional Time ◽  
Fracture Pressure ◽  
Increased Risk ◽  
Zonal Isolation ◽  
Operating Window

Abstract Successfully cementing production casing strings is one of the main challenges of well construction in mature fields. The implementation of cementing best practices can be difficult in the narrow pore pressure-fracture pressure (PPFG) window associated with reservoir depletion and complex well architecture. The increased risk of losses can lead operating teams to compromise on these best practices, often jeopardizing the zonal isolation objectives. This can result in significant additional time, cost, and production deferral/loss. Managed pressure cementing (MPC) is a viable technique to address these challenges. Using the managed pressure drilling (MPD) system's capability to precisely control bottomhole pressure, coupled with the use of mud weights that are lower than conventionally needed can expand the PPFG window; enabling operating teams to achieve a higher success rate in meeting the zonal isolation objectives. This paper will offer an optimized design methodology and critical considerations and parameters for MPC operations. It will also briefly describe the primary applications of MPC and specific, unique design considerations associated with each, namely, (1) mud weight less than pore pressure (PP), (2) losses prevention, and (3) wellbore stability control. Lastly, it will provide a case history illustrating how MPC was used in one of the operator's mature fields, by giving an overview of the job engineering design process, the operational planning (inclusive of contingencies), and the key highlights and learnings observed during execution.

Transient Coupling of Swab/Surge Pressure and In-Situ Stress for Wellbore-Stability Evaluation During Tripping

SPE Journal ◽  
2018 ◽  
Vol 23 (04) ◽  
pp. 1019-1038 ◽  
Author(s):  
Feifei Zhang ◽  
Yongfeng Kang ◽  
Zhaoyang Wang ◽  
Stefan Miska ◽  
Mengjiao Yu ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Pore Pressure ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Pressure Oscillations ◽  
Deepwater Drilling ◽  
Wellbore Pressure ◽  
Operating Window ◽  
Safe Operating

Summary This paper identifies wellbore-stability concerns caused by transient swab/surge pressures during deepwater-drilling tripping and reaming operations. Wellbore-stability analysis that couples transient swab/surge wellbore-pressure oscillations and in-situ-stress field oscillations in the near-wellbore (NWB) zone in deepwater drilling is presented. A transient swab/surge model is developed by considering drillstring components, wellbore structure, formation elasticity, pipe elasticity, fluid compressibility, fluid rheology, and the flow between wellbore and formation. Real-time pressure oscillations during tripping/reaming are obtained. On the basis of geomechanical principles, in-situ stress around the wellbore is calculated by coupling transient wellbore pressure with swab/surge pressure, pore pressure, and original formation-stress status to perform wellbore-stability analysis. By applying the breakout failure and wellbore-fracture failure in the analysis, a work flow is proposed to obtain the safe-operating window for tripping and reaming processes. On the basis of this study, it is determined that the safe drilling-operation window for wellbore stability consists of more than just fluid density. The oscillation magnitude of transient wellbore pressure can be larger than the frictional pressure loss during the normal-circulation process. With the effect of swab/surge pressure, the safe-operating window can become narrower than expected. The induced pore pressure decreases monotonically as the radial distance increases, and it is limited only to the NWB region and dissipates within one to two hole diameters away from the wellbore. This study provides insight into the integration of wellbore-stability analysis and transient swab/surge-pressure analysis, which is discussed rarely in the literature. It indicates that tripping-induced transient-stress and pore-pressure changes can place important impacts on the effective-stress clouds for the NWB region, which affect the wellbore-stability status significantly.

Increasing Plug and Abandon Efficiency in East Africa: Challenges and Solutions

2016 ◽  
Author(s):  
Galen Joneja ◽  
Michael Awalt ◽  
Carl Johnson ◽  
Martijn Bogaerts ◽  
MHD Tareq Alsam
Keyword(s):  
Best Practices ◽  
East Africa ◽  
Operating Costs ◽  
Additional Time ◽  
Operational Costs ◽  
Single Operation ◽  
Drilling Operations ◽  
Zonal Isolation ◽  
Well Abandonment ◽  
Cement Plug

ABSTRACT In line with an escalation of drilling operations in East Africa, operators and service contractors are increasing their focus on how to make operations more efficient in challenging market. One operation for which a robust, safe, and effective tool was utilized to increase efficiency is the plug and abandonment of deepwater exploration wells in Tanzania and Kenya. Traditional abandonment of a well is accomplished by stacking multiple cement plugs to achieve zonal isolation. The plugs covering reservoir sections are normally independently verified in keeping with best practices applicable to well barriers. By setting longer plugs to cover multiple zones, rig time and operating costs can be significantly reduced. However, there are limitations to cement plug length when set conventionally without significantly increasing the risk of stuck pipe. The Hydraulic Tubing Release Tool (HTRT) was introduced during a deep-water exploration campaign in East Africa. It has been used successfully during the abandonment of five different wells where seven plug and abandonment operations placed long abandonment plugs, ranging from 405m to 1787m, in a single operation. The utilization of the tubing release tool system in well abandonment operations has proved to lower the risks and operational costs through the reduction of necessary cementing operations. With the sacrificial tubing being left in the cement, there is less risk of plug contamination which occurs as a result of pulling out of the plug. It also allows for longer plugs to be set in a single operation as opposed to stacking several cement plugs to get the required length, saving additional time. It has been used successfully on five deepwater wells in East Africa to set long abandonment plugs in open holes ranging from 700m to 1800m MD. The main objective of the disconnect system is to shorten the time taken to perform a well abandonment program as well as reducing the associated risks, thereby saving rig time and money.

Impact of High Resolution 3D Geomechanics on Well Optimization in the Southern Gulf of Suez, Egypt

2021 ◽  
Author(s):  
Mohamed Elkhawaga ◽  
Wael A. Elghaney ◽  
Rajarajan Naidu ◽  
Assef Hussen ◽  
Ramy Rafaat ◽  
...  
Keyword(s):  
High Resolution ◽  
Pore Pressure ◽  
Cost Optimization ◽  
Oil Field ◽  
Wellbore Stability ◽  
Gulf Of Suez ◽  
Geomechanical Model ◽  
3D Geomechanical Model ◽  
The Cost ◽  
The Impact

Abstract Optimizing the number of casing strings has a direct impact on cost of drilling a well. The objective of the case study presented in this paper is the demonstration of reducing cost through integration of data. This paper shows the impact of high-resolution 3D geomechanical modeling on well cost optimization for the GS327 Oil field. The field is located in the Sothern Gulf of Suez basin and has been developed by 20 wells The conventional casing design in the field included three sections. In this mature field, especially with the challenge of reducing production cost, it is imperative to look for opportunites to optimize cost in drilling new wells to sustain ptoduction. 3D geomechanics is crucial for such cases in order to optimize the cost per barrel at the same time help to drill new wells safely. An old wellbore stability study did not support the decision-maker to merge any hole sections. However, there was not geomechanics-related problems recorded during the drilling the drilling of different mud weights. In this study, a 3D geomechanical model was developed and the new mud weight calculations positively affected the casing design for two new wells. The cost optimization will be useful for any future wells to be drilled in this area. This study documents how a 3D geomechanical model helped in the successful delivery of objectives (guided by an understanding of pore pressure and rock properties) through revision of mud weight window calculations that helped in optimizing the casing design and eliminate the need for an intermediate casing. This study reveals that the new calculated pore pressure in the GS327 field is predominantly hydrostatic with a minor decline in the reservoir pressure. In addition, rock strength of the shale is moderately high and nearly homogeneous, which helped in achieving a new casing design for the last two drilled wells in the field.

Effect of Drilling Fluid Temperature on Formation Fracture Pressure Gradient

2021 ◽  
Author(s):  
Ahmed Mostafa Samak ◽  
Abdelalim Hashem Elsayed
Keyword(s):  
High Temperature ◽  
Pressure Gradient ◽  
Thermal Effect ◽  
Drilling Fluid ◽  
Wellbore Stability ◽  
Cooling Effect ◽  
Fluid Temperature ◽  
Lost Circulation ◽  
Fracture Pressure ◽  
Downhole Temperature

Abstract During drilling oil, gas, or geothermal wells, the temperature difference between the formation and the drilling fluid will cause a temperature change around the borehole, which will influence the wellbore stresses. This effect on the stresses tends to cause wellbore instability in high temperature formations, which may lead to some problems such as formation break down, loss of circulation, and untrue kick. In this research, a numerical model is presented to simulate downhole temperature changes during circulation then simulate its effect on fracture pressure gradient based on thermo-poro-elasticity theory. This paper also describes an incident occurred during drilling a well in Gulf of Suez and the observations made during this incident. It also gives an analysis of these observations which led to a reasonable explanation of the cause of this incident. This paper shows that the fracture pressure decreases as the temperature of wellbore decreases, and vice versa. The research results could help in determining the suitable drilling fluid density in high-temperature wells. It also could help in understanding loss and gain phenomena in HT wells which may happen due to thermal effect. The thermal effect should be taken into consideration while preparing wellbore stability studies and choosing mud weight of deep wells, HPHT wells, deep water wells, or wells with depleted zones at high depths because cooling effect reduces the wellbore stresses and effective FG. Understanding and controlling cooling effect could help in controlling the reduction in effective FG and so avoid lost circulation and additional unnecessary casing points.

Obtaining Zonal Isolation in Geothermal Wells

2021 ◽  
Author(s):  
Allam Putra Rachimillah ◽  
Cinto Azwar ◽  
Ambuj Johri ◽  
Ahmed Osman ◽  
Eric Tanoto
Keyword(s):  
Best Practices ◽  
Oil And Gas ◽  
Lessons Learned ◽  
Free Fluid ◽  
High Heating Rate ◽  
Lost Circulation ◽  
Geothermal Well ◽  
Geothermal Wells ◽  
Zonal Isolation ◽  
Primary Cementing

Abstract Cementing is one of the sequences in the drilling operations to isolate different geological zones and provide integrity for the life of the well. As compared with oil and gas wells, geothermal wells have unique challenges for cementing operations. Robust cementing design and appropriate best practices during the cementing operations are needed to achieve cementing objectives in geothermal wells. Primary cementing in geothermal wells generally relies on a few conventional methods: long string, liner-tieback, and two-stage methods. Each has challenges for primary cementing that will be analyzed, compared, and discussed in detail. Geothermal wells pose challenges of low fracture gradients and massive lost circulation due to numerous fractures, which often lead to a need for remedial cementing jobs such as squeeze cementing and lost circulation plugs. Special considerations for remedial cementing in geothermal wells are also discussed here. Primary cement design is critical to ensure long-term integrity of a geothermal well. The cement sheath must be able to withstand pressure and temperature cycles when steam is produced and resist corrosive reservoir fluids due to the presence of H2S and CO2. Any fluid trapped within the casing-casing annulus poses a risk of casing collapse due to expansion under high temperatures encountered during the production phase. With the high heating rate of the geothermal well, temperature prediction plays an important part in cement design. Free fluid sensitivity test and centralizer selection also play an important role in avoiding mud channeling as well as preventing the development of fluid pockets. Analysis and comparison of every method is described in detail to enable readers to choose the best approach. Massive lost circulation is very common in surface and intermediate sections of geothermal wells. On numerous occasions, treatment with conventional lost-circulation material (LCM) was unable to cure the losses, resulting in the placement of multiple cement plugs. An improved lost circulation plug design and execution method are introduced to control massive losses in a geothermal environment. In addition, the paper will present operational best practices and lessons learned from the authors’ experience with cementing in geothermal wells in Indonesia. Geothermal wells can be constructed in different ways by different operators. In light of this, an analysis of different cementing approaches has been conducted to ensure robust cement design and a fit-for-purpose cementing method. This paper will discuss the cementing design, equipment, recommendations, and best available practices for excellence in operational execution to achieve optimal long-life zonal isolation for a geothermal well.

Simulating the effect of subsurface stresses and transient pore pressure on wellbore stability in subsea horizontal wells

2019 ◽  
Vol 41 (16) ◽  
pp. 2028-2038
Author(s):  
Ubedullah Ansari ◽  
Cheng YuanFang ◽  
Li QingChao ◽  
Georgia George Mawaipopo ◽  
Jia Wei
Keyword(s):  
Pore Pressure ◽  
Horizontal Wells ◽  
Wellbore Stability
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