Lessons Learnt from a Successful Sampling While Drilling Campaign Delivering Formation Oil Samples and Saturation Pressure Measurements in High H2S Carbonates

2021 ◽  
Author(s):  
Khalid Javid ◽  
Guido Carlos Bascialla ◽  
Alvaro Sainz Torre ◽  
Hamad Rashed Al Shehhi ◽  
Viraj Nitin Telang ◽  
...  
Keyword(s):  
Saturation Pressure ◽  
Carbonate Reservoir ◽  
Closed Chamber ◽  
Well Control ◽  
Pilot Hole ◽  
Fluid Identification ◽  
Pressure Testing ◽  
Lessons Learnt ◽  
Fluid Sampling ◽  
Complex Well

Abstract As island development strategies gain focus for capitalizing deep offshore assets, limitations like fixed slot location bring about the need for drilling extended reach (ERD) wells with multiple drain holes and complex well geometry to maximize the reservoir coverage for increased production. Pressure testing and reservoir fluid sampling operations require long stationary time and pose a risk of differential sticking. Deploying a pressure testing and fluid sampling tool into the drilling bottom-hole assembly (BHA) helps in maintaining well control through continuous circulation and providing measures to retrieve the tool by rotation and jarring in case of pipe sticking. This paper presents the successful deployment of sampling while drilling tools in three ERD wells drilled using water based and oil based muds to acquire representative formation oil samples from a high H2S carbonate reservoir. The formation oil samples were collected immediately after drilling the well to the target depth for limiting the invasion to collect clean samples in shorter pump-out volume and time. After securing the samples, a phase separation test was performed by fluid expansion in a closed chamber to measure the saturation pressure of the oil. A 30-min long pressure build up was also performed for pressure transient analysis to estimate permeability. Formation fluid samples were collected, while pulling out the drilling BHA, within 12-48 hours of drilling the well by pumping out 100-170 liters of fluid from the formation in 4-6 hours. During clean up, absorbance spectroscopy identifies the fluid phases – gas, oil and water. Prominent trends observed in compressibility, mobility, sound slowness and refractive index measurements add confidence to the fluid identification and provide accurate contamination measurements. Single-phase tanks charged with nitrogen were used to assure quality samples for PVT analysis. The sample tanks are made of MP35N alloy and the flow lines are made of titanium that are both H2S resistant and non-scavenging materials and hence, a separate coat of non-scavenging material was not required. In highly deviated wells, sampling while drilling technology can close the gaps of the conventional wireline operation on pipe conveyed logging in addition to saving 5-days of rig time by eliminating the need for conditioning trips, a dedicated run for pressure testing and sampling and minimizing the risk of stuck pipe and well control incidents The results from downhole fluid analysis and PVT lab are compared in this paper. Going forward, this technology can eliminate the requirement of a pilot hole for pressure testing & sampling by enabling sampling in complex well geometries in landing sections and ERD wells. The paper concludes with discussions on suggested improvements in the tool design and capability and recommendations on best practices to align with the lessons learnt in this sampling while drilling campaign.

Reservoir Fluid Mapping While Drilling: Untapping the Barents Sea

2021 ◽  
Author(s):  
Maria Cecilia Bravo ◽  
Yon Blanco ◽  
Mauro Firinu ◽  
Tosi Gianbattista ◽  
Eriksen Martin ◽  
...  
Keyword(s):  
Data Acquisition ◽  
Reservoir Characterization ◽  
Barents Sea ◽  
Hydrocarbon Composition ◽  
Hydrocarbon Exploration ◽  
Fluid Type ◽  
Pilot Hole ◽  
Fluid Identification ◽  
The Barents Sea ◽  
Petrophysical Evaluation

Abstract In complex and sensitive environments such as the northern Barents Sea, operations face multiple challenges, both technically and logistically. The use of logging while drilling (LWD) technology mitigates risks and assures acquisition of formation evaluation data in a complex trajectory. All data gathering was performed in LWD and provided the kernel for interpretation; alternate scenarios utilizing pipe conveyed wireline elevated risk factors as well as higher overall costs. Novel technology was required for this data acquisition, including fluid mapping while drilling (FMWD) that allows fluid identification with the use of downhole fluid analysis (DFA) using optical spectrometry as well as the retrieval of downhole fluid samples and a unique sourceless multifunction LWD tool delivering key data for the petrophysical evaluation. This paper presents a case study of the first application of a combination of FMWD and a petrophysical LWD toolstring in the Barents Sea. An excellent contribution to the operator of the PL229 that have pushed the boundaries of the formation sampling while drilling and set the basis to challenge the potentiality of this technique and improve the knowledge of the methodology that are the ultimate goals of this paper. Methods, procedures, process Hydrocarbon exploration, production, and transport in the Barents Sea are challenging. The shallow and complex reservoirs are at low temperature and pressure, potentially with gas caps. The Goliat field is the first offshore oil development in this environment, producing from two reservoirs: Realgrunnen and Kobbe. As part of the Goliat field infill drilling campaign with the aim of adding reserves and increase production, PL229 license operator drilled a highly deviated pilot hole to confirm hydrocarbons contacts in the undrained Snadd formation, which lie between two producing reservoirs. A successful data acquisition would not only provide information on the structure of the reservoir but would also assess the insitu movable fluid: type of hydrocarbon or water. FMWD allowed insitu fluid identification with the use of DFA, enabling RT evaluation of hydrocarbon composition as well as the filtrate contamination prior to filling the sampling bottles for further laboratory analysis. All data was acquired while drilling and using a comprehensive real-time visualization interface. Results, observation, conclusion Extensive prejob planning was conducted to optimize the operation. Dynamic fluid invasion simulations were used to estimate the required cleanup times to reach low contaminations. Simulations showed there was significant advantage in cleanup times when sampling soon after drilling. Honoring the natural environment, a unique sourceless multifunction LWD tool was used to acquire data for petrophysical evaluation-GR, resistivity, radioisotope-free density and neutron porosity, elemental capture spectroscopy, and sigma. Fluid mapping in a single run was key to efficiently resolve the insitu fluid type and composition. Critical hydrocarbon samples were collected soon after the formation was drilled to minimize mud filtrate invasion and reduce cleanup times. Multiple pressure measurements were acquired and six downhole fluid samples at low contamination (∼3% confirmed by laboratory) collected at several stations in variable mobilities. One scanning station was done at a zone were a physical sample was not required to confirm absence of gas cap. The DFA capabilities and ability to assess composition and control the fluid cleanup from surface allowed critical decisions to complete the acquisition program in this remote complex environment, all while drilling. In conclusion, FMWD results facilitated the placement decisions of the horizontal drain in this reservoir. This green BHA is unique in the LWD world. It eliminates radioactive source-handling and all related environmental risks to provide a comprehensive reservoir characterization. FMWD contributes formation pressure and fluid characterization and enables the physical capture of fluid samples in a single run. The combination of these two technologies completed the formation and fluid evaluation needs in this remote and environmentally sensitive area while drilling.

Operational efficiency improvement by using logging while drilling (LWD) fluid sampling and pressure-testing device

2014 ◽  
Vol 54 (2) ◽  
pp. 543
Author(s):  
Steve J Martin ◽  
Pei-Chea Tran ◽  
Steven Marshall
Keyword(s):  
Risk Mitigation ◽  
Sample Volume ◽  
Asia Pacific ◽  
Testing Device ◽  
Major Step ◽  
Chemical Absorption ◽  
Pressure Testing ◽  
Chemical Content ◽  
Hydrocarbon Gas ◽  
Fluid Sampling

Abstract An operator in Asia Pacific required a large sample volume from a gas reservoir for accurate non-hydrocarbon gas (NHCG) content analysis from two extended reach wells. This extended abstract highlights the use of an LWD fluid sampling and formation pressure-testing device to overcome numerous challenges, including a highly deviated wellbore, stuck pipe, oil-based mud (OBM) gas-sampling issues, and prevention of geo-chemical absorption. Application The choice to use an LWD fluid sampler was based on several factors that reduced significant risks. Due to the well’s deviated nature, the only traditional wireline fluid sampling solution would have required a pipe-conveyed logging mechanism. This would have added rig days to the project and increased the risk of stuck pipe. To prevent geo-chemical absorption, the storage tanks were manufactured with a specialised metallurgic design. This would be tested by applying a customer-requested coating to half the tanks and monitor differences in geo-chemical content. To prevent differential sticking, testing sequences would be limited to 90-minute intervals. Results, observations, and conclusions After two runs in separate wells, a total of 25 samples were acquired containing more than 19 litres of fluid. Due to the reduced invasion profile as a result of LWD technology, fluid stability was reached within the 90-minute threshold. Furthermore, results showed only 8% OBM contamination—half the amount seen in offsets from wireline produced fluid samples. Finally, due to the improved operation efficiency and the quality of the samples, the customer estimates that it saved nearly $10 million in rig costs and millions more in reduced retrofitting costs of the production facility. Significance of subject matter This extended abstract highlights a major step-change in fluid sampling technology. Operators no longer need to consider a well’s deviation in the ability to collect fluid samples. The recap of the two wells will offer additional best practices and risk mitigation techniques for future LWD sampling projects. It also adds yet another LWD technology that provides consistent wireline equivalent data.

Reservoir-Fluid Sampling Revisited - A Practical Perspective

2007 ◽  
Vol 10 (06) ◽  
pp. 589-596 ◽  
Author(s):  
Johannes Bon ◽  
Hemanta Kumar Sarma ◽  
Jose Teofilo Rodrigues ◽  
Jan Gerardus Bon
Keyword(s):  
Oil Recovery ◽  
Economic Value ◽  
Saturation Pressure ◽  
Sulfur Compounds ◽  
Second Phase ◽  
Plant Design ◽  
Reservoir Fluid ◽  
Well Conditioning ◽  
Sampling Procedures ◽  
Fluid Sampling

Summary Pressure/volume/temperature (PVT) fluid properties are an integral part of determining the ultimate oil recovery and characterization of a reservoir, and are a vital tool in our attempts to enhance the reservoir's productive capability. However, as the experimental procedures to obtain these are time consuming and expensive, they are often based on analyses of a few reservoir-fluid samples, which are then applied to the entire reservoir. Therefore, it is of utmost importance to ensure that representative samples are taken, as they are fundamental to the reliability and accuracy of a study. Critical to the successful sampling of a reservoir fluid is the correct employment of sampling procedures and well conditioning before and during sampling. There are two general methods of sampling—surface and subsurface sampling. However, within these, there exist different methods that can be more applicable to a particular type of reservoir fluid than to another. In addition, well conditioning can differ depending on the type of reservoir fluid. Sampling methods for each reservoir type will be discussed with an emphasis on scenarios where difficulties arise, such as near-critical reservoir fluids and saturated reservoirs. Methods, including single-phase sampling and isokinetic sampling, which have been used increasingly in the last decade, will also be discussed with some detail, as will preservation of the representatives of other components in the sample including asphaltenes, mercury, and sulfur compounds. The paper presents a discussion aimed at better understanding the methods available, concepts behind the methods, well conditioning, and problems involved in obtaining representative fluid samples. Introduction Reservoir-fluid samples are obtained for a number of reasons, includingPVT analysis for subsequent engineering calculationsDetermination of the components that exist in a particular reservoir to have an understanding of the economic value of the fluidKnowledge of the contents of certain components that exist in the reservoir fluid for further planning and future drilling programs, such as the content of sulfur compounds and carbon dioxide, and the corrosiveness of the fluid. This will have an impact on the material used for casing, tubing, and surface equipment that may be necessaryKnowledge of the fluid's ability to flow through production tubing, pipelines, and other flow lines, and possible problems that may arise because of viscosity changes because of precipitation of solids such as wax and/or of asphalteneDetermining the contaminating components that affect plant design, such as the mercury content, sulfur components, and radioactive componentsIf the saturation pressure is approximately equal to the reservoir pressure then a second phase may be present. This is particularly relevant for gas reservoirs, where further drilling may discover an oil or condensate leg. Mostly the samples are required to obtain a better knowledge of a combination of these effects; however, it must be kept in mind that often the sample is not required to resolve all of these issues.

Well Design for Subsea Exploration Drilling in Shallow Formations of Barents Sea

2021 ◽  
Author(s):  
Mikolaj Stanislawek
Keyword(s):  
Design Process ◽  
Barents Sea ◽  
Weather Conditions ◽  
Design Approach ◽  
Drilling Process ◽  
Well Control ◽  
Pilot Hole ◽  
Planning Phase ◽  
Well Design ◽  
Exploration Drilling

Abstract Subsea exploration drilling in relatively new and not yet fully recognized frontiers like Barents Sea continues to be a focus for Oil & Gas Companies. Safety and robust well barriers are important as ever. This paper describes well design process and execution of a challenging subsea exploration well in shallow formations of Barents Sea by Equinor. Case study for planning and well design process is presented, followed by drilling experiences during execution. Several well design concepts and contingency scenarios that were evaluated and risk assessed in the planning phase are presented, which required extra focus on well design and well barriers. Compensating measures along with high focus on well control and well barriers in shallow drilling environment of Barents Sea were developed during planning phase of this well, and reviewed with planning and execution teams. Design approach encompasses casing design in shallow reservoir well with narrow margin between required formation integrity and fracture pressures, low kick tolerance, drilling in unstable formations, low temperature and pressures. Robust well design in shallow and weak formations is feasible with conventional casing design approach, and well challenges can be overcome by proper planning and contingency measures involving additional preparation of drilling crew, and by use of advanced drilling technology and procedures. Safety and well control is the most important factor in well design. Relevant contingency scenarios should be prepared with equipment and procedures in place. Importance of drilling a pilot hole in unrecognized area near main well and its influence on main well design is crucial. This is a good example of planning and drilling process for challenging well in unrecognized area with limited reference well data, challenging logistics, and weather conditions of Barents Sea. It will demonstrate how many contingency scenarios were fully prepared in planning phase and their rationale, versus encountered drilling experiences, to be a more precise reference for future wells in the area.

A Success Story of Critical Data Gathering During the Development Phase of Extreme ERD Well Drilling

2021 ◽  
Author(s):  
Atul Kumar Anurag ◽  
Adel Alkatheeri ◽  
Alvaro Sainz ◽  
Khalid Javid ◽  
Yaxin Liu ◽  
...  
Keyword(s):  
Decision Making ◽  
Real Time ◽  
Drill String ◽  
Carbonate Reservoir ◽  
Carbonate Reservoirs ◽  
Development Phase ◽  
Formation Pressure ◽  
Pressure Testing ◽  
Critical Data ◽  
Well Trajectory

Abstract This paper discusses a holistic combination of advanced formation evaluation techniques with pressure testing and reservoir navigation services to mitigate uncertainty related challenges in real time and successfully drill & place ERD laterals targeting Jurassic carbonate reservoirs. A meticulously planned approach to navigate the well trajectory by tracking the desired properties, informed decision-making while drilling and accurate data acquisition for aiding appropriate selection and placement in-flow control device (ICD) in lower completion design and future reservoir management contributed to the success of these complex wells in carbonate reservoirs. The first well in this study, involved drilling and evaluating a long lateral section as single oil producer targeting a carbonate reservoir. While no tar presence was expected, a combination of density, neutron porosity and nuclear magnetic resonance (NMR) logs while drilling resulted in identifying a deficit NMR porosity when compared to density porosity. Deployment of a formation pressure testing while drilling (FPWD) tool enabled measurement of the formation mobility and validate the presence of a tar. Using the same combination of measurements in the subsequent wells for delineating the tar enabled accurate planning of injection wells on the periphery of the field. Approximately 3 days were saved compared to the first well where the drill string had to be POOH to run-in with FPWD service. Hence, having FPWD tool in the same string helped in confirming the formation mobility in real time to call for critical decision making like changing the well trajectory or calling an early TD. Across all the wells drilled in this field, the formation pressure, mobility and porosity measurements provided valuable input for optimum ICD placement and design. Successful identification of unexpected tar resulted in substantial rig time savings, accurate planning of asset utilization and added confidence in design and placement of lower completions by utilizing LWD data. Benefits of integrated data and services combination became clear for applications involving advanced reservoir characterization and enhanced well placement in complex carbonate reservoirs. From the offset wells, a tar was seen in deeper formations but the integration of LWD NMR and mobility data from this well confirmed the presence of a tar within the zone of interest. The study established a cost-effective workflow for mitigating uncertainties related to tar encountered while drilling extreme ERD laterals in an offshore environment where any lost time results in significant increase in expenditures during the development phase. A systematic approach to tackle these uncertainties along with acquisition of critical data for the design & placement of completion results in optimum production from the reserves.

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