Kumar, Abhineet (Cairn Oil & Gas, Vedanta Limited) | Prakash, Aditya (Cairn Oil & Gas, Vedanta Limited) | Singh, Alok (Cairn Oil & Gas, Vedanta Limited) | Bharati, Pradeep (Cairn Oil & Gas, Vedanta Limited) | Jayan, Binshu (Cairn Oil & Gas, Vedanta Limited) | Kothiyal, Manish (Cairn Oil & Gas, Vedanta Limited) | Patil, Bhushan (Cairn Oil & Gas, Vedanta Limited) | Sarma, Phanijyoti (Cairn Oil & Gas, Vedanta Limited)
An offshore drilling campaign comprising of four development wells was conducted to augment oil production from a field located off the western coast of India. All four wells were designed to be sidetracked from existing depleted wells of the field. Historically, preparing existing wells in the field for side-track took ~4 days/well of a drilling rig and associated spread cost. This paper presents a case- history of conducting side-track well preparatory activities by a rig-less well intervention spread leading to significant time and cost savings. This method was also the first instance of such an activity being conducted in an offshore environment in India.
Prior to actual side-track drilling from an existing well in a brown field, it is required to abandon the open zones in the existing well and prepare the well for casing window cutting for further drilling to a new sub-surface target. Typical preparation activities include multiple wireline runs to set/retrieve deep set and tubing hanger plugs, well killing, nipple-down X-mas tree, nipple-up BOP, wireline run to cut tubing, retrieval of existing completion and ultimately placement of cement plugs to abandon the parent wellbore. The routine approach in the organization for all previous offshore drilling campaigns was to utilize the offshore drilling rig for afore-mentioned well preparation activities. Substantial rig time was spent incurring the cost of entire rig spread for an average ~4 days/well equivalent to ~40% of total well completion time.
The paper elaborates on rig-less operations set-up consisting of Cementing and Wireline Units utilized to conduct well killing, placement of cement plugs, production tubing cutting and nippling down X-mas tree prior to the mobilization of the drilling rig at the platform. The only operation left for the drilling rig was to pull-out the existing completion string and then drilling operations could commence.
The execution of planned operations was flawless on three wells while one well posed technical limitation due to its high deviation. The rig less well preparation campaign was concluded incident free, ahead of schedule and within budget. This offline exercise prior to rig-move saved ~12 days of drilling campaign time which helped in cutting down on overall drilling campaign cost and also allowed the flexibility of adding more wells to the campaign within fair weather window.
While this was an effort to simplify operations and save costly drilling rig-time in a side-track drilling campaign by conducting some very critical operations offline, these methods can also be adopted for planning well abandonment and decommissioning activities in a mature field.
The negative impacts of high water cut in mature fields are well known within the oil & gas industry. Water production preventive & mitigative measures are well established and documented: Wireline or coil tubing conveyed diagnostic and work-over operation(s) is one of such common preventive measures. This paper, through a series of integrated case studies will highlight the best practices for wireline conveyed logging and work-overs with one common goal, i.e. to achieve the water production to a minimum acceptable level in deviated high water cut wells.
The prolific XYZ field is located in the Northern North Sea and it produces oil from Jurassic Brent Group. Oil production from the XYZ reservoir started in early 1978, with 43 producing wells and 15 water injection wells targeting the Rannoch, Etive, Ness and Tarbert sands. Oil and gas production peaked in 1982 and since then production has steadily declined for this field. The increasing water cut in the wells of this field is presenting a challenge for the operating companies.
Production profiling using advanced Production Logging data, casing/tubing integrity check using Multi-Finger Caliper data and saturation monitoring using cased-hole Reservoir Saturation data was done in these wells to ascertain the water producing zones and do the subsequent well intervention, if required. A strategic diagnostic test was designed to precisely evaluate the flow profile using advance production logging tool consisting of 5 mini-spinners & 6 sets of each electrical and optical probes; Real-time data assessment and analysis was done for different flowing rate surveys to validate the findings. Additionally, casing condition was evaluated using Multi-Finger Caliper to decide Plug or Straddle setting depths. Also, new hydrocarbon bearing zones were identified based on cased-hole saturation tool results. The analysis results boosted the cumulative oil production.
This study demonstrates the importance of making real time interpretation decisions at the wellsite and the benefit of developing a good working relationship between wellsite engineers and onshore technical support. The results of this work led to the unequivocal determination of major oil and water producing zones in deviated high water cut (95%+) wellbores which further helped in taking workover decisions to carry out water shut off, utilizing either plug or straddle technology. The findings of caliper data determined the appropriate plug or straddle setting depths. The results were compared and confirmed with the nearby well dynamic pressures and production data.
The technical approach and processes applied to wells of XYZ field is a valuable example guide to decide water shut off zones and technique of similar plays. This study consists of three integrated case studies from a mature field where water shut-off zones and technologies were decided based on the findings of production logging and well integrity data. Also, re-perforation jobs were performed based on the cased-hole reservoir saturation data results. These strategic workover operations ultimately led to significant increase in hydrocarbon production.
Lin, Qingyang (Imperial College London) | Bijeljic, Branko (Imperial College London) | Krevor, Samuel C. (Imperial College London) | Blunt, Martin J. (Imperial College London) | Rücker, Maja (Imperial College London) | Berg, Steffen (Imperial College London / Shell Global Solutions International BV) | Coorn, Ab. (Shell Global Solutions International BV) | van der Linde, Hilbert (Shell Global Solutions International BV) | Georgiadis, Apostolos (Shell Global Solutions International BV) | Wilson, Ove B. (Shell Global Solutions International BV)
In the context of digital rock analysis, pore-scale imaging of multiphase flow experiments using X-ray microtomography can be used to obtain fundamental insights into pore-scale displacement physics. This provides a basis to better calibrate numerical pore-scale simulators, or it can be used to understand local fluid distributions, while simultaneously measuring average properties, equivalent to a traditional SCAL experiment. Imaging studies in the literature have historically been conducted on small water-wet plugs, using kerosene, or another refined oil, as the non-wetting phase. Prior to conducting waterflood experiments, the initial water saturation has been established by dynamic flooding. The disadvantage with this is that a nonuniform saturation profile is established due to the capillary end effect. This will result in a higher average initial water saturation compared with, for instance, standard SCAL techniques, such as the porous-plate method or centrifugation.
In this paper, a methodology for initializing multiple small rock samples to the same connate water saturation and wettability state has been developed by adopting best SCAL practices, namely the porous-plate method or centrifugation using crude oil, followed by aging. We drill multiple small plugs from a full-size SCAL core sample, without losing capillary continuity with the base of the original sample. In the example presented, for Bentheimer sandstone, the initial saturation was established using centrifugation. The experiment is designed to prevent a nonuniform saturation profile in the small plugs. We use in-situ imaging to determine the water saturation after primary drainage and show that it is indeed uniform across the sample with a value consistent with larger-scale SCAL measurements and the measured mercury-injection capillary pressure. We also show that a significant wettability alteration had occurred by measuring in-situ contact angles.
Brice Y. Kim and I. Yucel Akkutlu, Texas A&M University, and Vladimir Martysevich and Ronald G. Dusterhoft, Halliburton Summary The stress-dependent permeabilities of split shale core plugs from Eagle Ford, Bakken, and Barnett Formation samples are investigated in the presence of microproppants. An analytical permeability model is developed for the investigation, including the interactions between the fracture walls and monolayer microproppants under stress. The model is then used to analyze a series of pressure-pulsedecay measurements of the propped shale samples in the laboratory. The analysis provides the propped-fracture permeability of the samples and predicts a parameter related to the quality of the proppant areal distribution in the fracture. The proppant-placement quality can be used as a measure of success of the delivery of proppants into microfractures and to design stimulation experiments in the laboratory. Introduction Unconventional-oil/gas resources, such as tight gas/oil and resource shale, have low porosity and ultralow permeability. Creating a well-connected complex fracture network is a key component of increasing the permeability and accelerating production. The early era of hydraulic fracturing horizontal wells in unconventional formations was concerned with achieving long fractures with multistage treatments with large cluster spacing. However, recent trends in this type of well completion and stimulation involve fractures that are created in narrower clusters in much closer spacing, targeting larger surface areas. It is argued that the practice of hydraulic fracturing with narrow clusters in close spacing along a lateral wellbore creates fractures with significantly reduced sizes, but in a complex network (Rassenfoss 2017). The creation of a network of fractures includes major operational issues.
The objective of this study is to compare the laboratory behavior of natural (Mode II) and induced (Mode I and II) fractures during stress-dependent permeability tests (SDk) to verify under which conditions the hydraulic behavior of induced fractures may be assumed to be representative of that of in-situ natural fractures. Fracture modes are identified by the way the force that enables the crack to propagate is applied and may be of three different types. Mode I fractures (propagated by a tensile stress normal to the plane of the crack) and Mode II fractures (propagated by a shear stress acting parallel to the plane of the crack and perpendicular to the crack front) are of import in the present study. To test under which conditions this assumption may hold, cylindrical specimens of different rock types including plugs with an intact matrix and plugs with a natural fracture propagating through their body were selected. When possible, the plugs were grouped in pairs so as to form homogeneous sets characterized by a coherence in specific matrix properties (porosity, density, permeability), with each pair including a plug containing a natural fracture. Induced Mode I and Mode II fractures were then propagated axially through the intact specimens and each plug set was tested for SDk. All of the tests were run under similar triaxial test conditions.
Capillary pressure is a crucial step in reservoir properties definition and distribution during static and dynamic modelling. It is a key input into saturation height modelling (SHM) process, understanding the fluid distribution and into reservoir rock typing process. Capillary pressure models provide an insight into field dynamic for the identification of swept zones and provide another calibration besides the log calculated saturation. Capillary pressure curve tends to be more complex in carbonates in comparison to sandstone reservoirs because of post deposition processes that impact the rock flow properties, hence complex pore throat size distribution (uni-modal, bi-modal or tri-modal). Therefore, accurate determination of this property is the cornerstone in the reservoir characterization process.
Capillary pressure can be obtained using several experimental techniques, such as mercury injection (MICP), centrifuge (CF) and porous plate (PP). Each method has its own inherited advantages and disadvantages. The MICP method tends to be faster, cheaper and provides a full spectrum of pore throat size of a plug. Whereas, the PP method can be carried out at reservoir conditions with minimum required corrections.
In this paper, a detailed workflow for quality control capillary pressure is discussed. The workflow is sub-divided into three main parts: Instrumental and experimental level, core measurement level and logs level. Experimental level starts with proper designing the actual procedure of the capillary pressure experiment. Parameters such as pore volume, bulk volume and grain density are investigated at core measurement level. In geological-petrography montage, all petrography data; X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), thin section and computed tomography scan (CT) are used along with the capillary pressure curve for assessment. Comparing various methodologies of experimental technique carried out on twin plugs, if exist, are also investigated. The capillary pressure that passes the previous QC steps is used as input into saturation-point comparison as a logs level QC. The saturation calculated from capillary pressure is compared to log-derived water saturation eliminating any issues with porosity and permeability of the trims and provides insight to the uncertainty level in the model. As an additional step, the MICP measurements are fitted with bi-modal Gaussian basis functions with two practical benefits. First, the quality of this fitting is a useful indicator for the evaluation of pore structure complexity and the identification erroneous measurements. Second, the fitting parameters are useful inputs for geological interpretation, rock typing and SHM. This rapid and automated workflow is a useful tool for screening, processing and integration of large-scale capillary pressure data sets, a key step in integrated reservoir description, characterization and modelling.
Novel fibrous and particulate LCM products of variable mechanical characteristics and chemical composition were developed using physio-mechanical treatment and processing of various waste components of date palm trees available each year as pruning wastes, post crop harvesting wastes, waste generated after making cookies and confectioneries and also the waste arising due to the removal of deceased and nonproductive date trees. Experimental tests conducted using PPT apparatus at 500 and 1500 psi pressure and 250 F temperature using 2 mm slotted disc demonstrated the efficient sealing and blocking for all of the particulate and fibrous LCM products either immediately after the application of the overbalance pressure or after a while. Some of the LCM products showed instantaneous sealing capacity after the application of overbalance pressure. Several commercial LCM products were also tested and evaluated using the same concentration and test conditions for comparative assessment of the performance of the newly developed LCM products. Interestingly, all of the new LCM products showed similar or better performance than the equivalent commercial products. Engineered fiber blends developed using the date palm industry waste also showed similar or better performance than the commercial or currently used LCM blends. Experimental results also indicated the suitability of date palm industry waste in replacing some of the synthetic fibers used by the industry in commercial LCM blend design. All these experimental results indicate that the date palm industry wastes are potential sources of raw materials for various product development for oil and gas field applications.
As the scope of deepwater operations increases, the need for cost-effective well servicing is paramount, particularly because of the continued challenges associated with current volatile commodity pricing. One of the first requirements on any subsea deepwater intervention with a horizontal wellhead production tree is pulling the subsea horizontal tree isolation lock mandrel plugs, commonly referred to wellhead or crown plugs. This can be a "show stopper" event if not planned correctly. Because of the critical nature of this action, the majority of operators follow a two-prong approach, with a primary plan of action and a contingency procedure, to help ensure barrier removal proceeds as planned. Although successful removal of the crown plugs is the principal concern, it needs to be completed cost-effectively for the intervention to obtain approval.
The advent of digital slickline (DSL) allows surface readout (SRO) monitoring during the removal and installation of these barriers to provide an increased level of confidence during this important phase of the operation. This paper outlines case studies of the real-time sensors available with the RF communication DSL system that was highlighted previously (
Additionally, the straight pull battery operated extended-stroke downhole power unit highlighted in
New developments as the downhole power generator was ported to DSL are discussed, notably on- command motor controls and SRO, which was traditionally only available in memory. A downhole anchor was added to the toolbox, which can be run in combination with the downhole power generator to expand effectiveness, as new production trees might not allow for a no-go landing shoulder. To address the increased water depths, the 3.59-in. extended-stroke downhole power generator was upgraded to 80,000 lbf pulling force.
Vijay, Rachit (Cairn Oil and Gas,Vedanta Ltd) | Panigrahi, Nishant (Cairn Oil and Gas,Vedanta Ltd) | Khanna, Manu (Cairn Oil and Gas,Vedanta Ltd) | Kothiyal, Manish Dutt (Cairn Oil and Gas,Vedanta Ltd) | Sarma, P J (Cairn Oil and Gas,Vedanta Ltd) | Bohra, Avinash (Cairn Oil and Gas,Vedanta Ltd) | Tiwari, Shobhit (Cairn Oil and Gas,Vedanta Ltd) | Pinto, Thomas (Welltec)
The subject well is a recently drilled and completed in Cambay field offshore in West coast of India. After landing the completion, two mechanical plugs were installed to nipple down BOP and nipple up X-mas tree. The plugs were installed in a 3.875" tubing hanger profile and in a 3.813" SC-TRSSSV selective profile. The problem arose while retrieving the 3.813" selective plug with 4" GS tool after installation of X-mas tree. The slickline wire snapped while doing the jarring operations resulting in fish in the well with BHA and plug slipping down below the selective profile. The plug fell inside the well and got stuck at the 4.5" × 3.5" tubing crossover joint ~20m below the SC-TRSSSV depth. The fished slickline wire along with the slickline tool-string BHA was successfully retrieved from the well, however, the plug remained stuck at the 4.5" × 3.5" tubing cross-over and could not be fished out even after several conventional approaches with slickline.
Solutions involving rig based retrieval and rig less coil tubing intervention and e-line robotic technology for retrieval of the plug were evaluated. Upon completion of a detailed feasibility study of available options, it was decided to conduct fishing of the plug with e-line based advanced robotic well intervention techniques such as eline miller, tractor and stroker. Unique milling bits were designed and customized for this operation. The milling operation involved multiple runs to target the removal of various parts of the struck lock mandrel. Upon successful milling operation, it was planned to retrieve the plug with slickline.
Initial attempts to retrieve the plug by straight pull using 33k pulling capacity Eline Stroker were unsuccessful. Subsequently, milling was attempted with a combination of E-line tractor and Miller to drill thru the plug. The milling initially started as per the plan but after 3 inches of milling the bit got stalled and was eventually stuck inside the plug. The E-line BHA had to be released from the mechanical disconnect sub above the bit. A modified 2" UPT tool with E-line tractor-stroker was run to fish out the bit and plug which resulted in the plug getting released from the stuck position and moving upwards about 10-meter from the stuck depth. Once this was accomplished, plug and bit were successfully retrieved with slickline.
The paper details the background of the stuck incident, selection methodology of fishing technique, fishing work plan and its successful execution. The paper also describes the operational difficulties encountered and the mitigation chosen while milling a plug with an electric line in the offshore environment.
With the objective of increasing productivity and achieving an economically sustainable development of the non-conventional reservoirs in Argentina, the oil and gas (O&G) energy companies are focused on drilling horizontal wells with lateral extensions between 2500 m (8,200 ft) to 3000 m (9,840 ft) in length. In order to produce commercial volumes of hydrocarbons, it is mandatory to fracture-stimulate multiple zones. The "plug and perf" method continues to be the most common completion technique in the field. Once the stimulation is completed, a coiled tubing (CT) milling operation is undertaken to remove the frac plugs. Critical to achieving a successful operation is reaching total depth (TD) in the well with the coiled tubing. The precise determination of the operational coefficient of friction (CoF) between the coiled tubing string and the production casing, could be the difference between failure and success, affecting both the technical and economical results of the project. The goal of this paper is to share the lessons learned after more than forty extended reach operations and the experience earned on the utilization of real time simulations to define both, the tensile load exerted for an extended reach tool and the coefficient of friction found during coiled tubing operations. Also demonstrate, by analyzing real life applications, how the implementation of this technology and new working methodology, allows to anticipate deviations with respect to the "normal" values of friction, achieve a better understanding of the influence of solids in the completion to the coefficient of friction and obtain a more efficient use of the metal-metal lubricant utilized during the milling operations.