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Collaborating Authors
Karimi, Moji
Applying Subsurface DNA Sequencing in Wolfcamp Shales, Midland Basin
Lascelles, Peter (EP Energy) | Wan, Jichun (EP Energy) | Robinson, Lauren (EP Energy) | Allmon, Randy (EP Energy) | Evans, Grant (EP Energy) | Ursell, Luke (Biota Technology) | Scott, Nicole M. (Biota Technology) | Chase, John (Biota Technology) | Jablanovic, Jelena (Biota Technology) | Karimi, Moji (Biota Technology) | Rao, Vik (Biota Technology)
Abstract DNA diagnostics is a new reservoir characterization tool with potential to maximize reservoir production in tight rock formations. DNA extracted from rock layers provides high resolution fingerprints that define a "DNA stratigraphy" for organic intervals like the Wolfcamp. DNA sequences originate from microbes feeding on organic matter or minerals within the formation. A DNA stratigraphic profile, or type section, was assembled from a vertical pilot well's cuttings and core. The DNA signature from produced oil from offset laterals was subsequently compared against the DNA type section to provide estimated effective drainage height. Cuttings from a lateral well were compared with DNA from its produced oil to construct a production profile comparable to a traditional production log. In addition, when oil samples are collected over time, the method provides insight on interference, completion effectiveness, and SRV (Stimulated Reservoir Volume) changes with time. An optimized development plan in unconventional reservoirs requires operators to understand parameters such as effective drainage height, hydraulic fracture half-length and individual stage contributions resulting from their completions. Wolfcamp reservoirs consist of highly laminated mudrocks interbedded with limestones that have quite different mechanical properties. These contrasting lithologies make it difficult to estimate resultant completion geometries, SRV, and well-to- well interactions. Also, using costly production logs, individual stage contributions are difficult to obtain in lower pressure reservoirs like the Wolfcamp. However, these reservoir performance parameters are required to set benchmarks and continuously uplift the EUR by taking advantage of insightful diagnostics. Production logs, micro-seismic, chemical or radioactive tracers are all useful in understanding the subsurface, but can be expensive and can pose operational challenges. Subsurface DNA sequencing is a relatively low cost new data source that can be used to gain subsurface insights in complicated reservoirs. DNA stratigraphy can help assess critical geometric parameters resulting from stimulation by employing non-invasive sampling that enables lifetime well monitoring to track the flow of oil and provide engineers the basis to optimize completions and development plans. An 8 well "subsurface" lab was selected for the experiment. The project included one vertical pilot hole with cuttings, and 8 horizontal wells landed in two Wolfcamp pay zones (one of the laterals was extended from the same vertical pilot). Three horizontals had been on production for 11 months before the pilot well and 6 additional laterals were drilled. The pilot well and its sidetracked lateral had cuttings extracted for DNA sequencing. DNA signatures from the pilot well and lateral well were compiled to produce vertical and lateral DNA stratigraphic profiles. The DNA stratigraphic profiles were then compared to DNA from oil produced in the 7 offset laterals. DNA profiles were also compared to standard geologic parameters using pilot well e-logs, particularly mechanical stratigraphy. Lateral wells were sampled at various times after initial production to assess changes with time. Blind tests were designed to check the method as a reasonable estimator for effective drainage height and communication. DNA stratigraphy provides a more informed view of well spacing, completion design and well performance to help increase efficiency and asset value.
- Geology > Petroleum Play Type > Unconventional Play > Shale Play > Shale Gas Play (1.00)
- Geology > Geological Subdiscipline > Stratigraphy (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.68)
- North America > United States > West Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Virginia > Appalachian Basin > Marcellus Shale Formation (0.99)
- North America > United States > Texas > West Gulf Coast Tertiary Basin > Eagle Ford Shale Formation (0.99)
- (44 more...)
Summary Drilling depleted reservoirs often encounters a host of problems leading to increases in cost and nonproductive time. One of these problems faced by drillers is lost circulation of drilling fluids, which can lead to greater issues such as differential sticking and well-control events. Field applications show that wellbore strengthening effectively helps reduce mud-loss volume by increasing the safe mud-weight window. Wellbore-strengthening applications are usually designed on the basis of induced-fracture characteristics (i.e., fracture length, fracture width, and stress-intensity factor). In general, these fracture characteristics depend on several parameters, including in-situ stress magnitude, in-situ stress anisotropy, mechanical properties, rock texture, wellbore geometry, mud weight, wellbore trajectory, pore pressure, natural fractures, and formation anisotropy. Analytical models available in the literature oversimplify the fracture-initiation and fracture-propagation process with assumptions such as isotropic stress field, no near-wellbore stress-perturbation effects, vertical or horizontal wells only (no deviation/inclination), constant fracture length, and constant pressure within the fracture. For more-accurate predictions, different numerical methods, such as finite element and boundary element, have been used to determine fracture-width distribution. However, these calculations can be computationally costly or difficult to implement in near-real time. The aim of this study is to provide a fast-running, semianalytical work flow to accurately predict fracture-width distribution and fracture-reinitiation pressure (FRIP). The algorithm and work flow can account for near-wellbore-stress perturbations, far-field-stress anisotropy, and wellbore inclination/deviation. The semianalytical algorithm is modeled after singular integral formulation of stress field and solved by use of Gauss-Chebyshev polynomials. The proposed model is computationally efficient and accurate. The model also provides a comprehensive perspective on formation-strengthening scenarios; a tool for improved lost-circulation-materials design; and an explanation of how they are applicable during drilling operation (in particular, through depleted zones). Sensitivity analysis included in this paper quantifies the effect of different rock properties, in-situ-stress field/anisotropy, and wellbore geometry/deviation on the fracture-width distribution and FRIP. In addition, the case study presented in this paper demonstrates the applicability of the proposed work flow in the field.
- North America > United States > California (0.28)
- North America > United States > Texas (0.28)
- Well Drilling > Wellbore Design > Wellbore integrity (1.00)
- Well Drilling > Pressure Management > Well control (1.00)
- Well Drilling > Drilling Fluids and Materials (1.00)
- (2 more...)
Abstract The aim of this study is to present an integrated and analytical workflow which includes the following execution steps: 1) generating a geomechanical model for the wellbore based on input data from different sources; 2) determining the stress tensor around the wellbore based on a transient thermo-poro-elastic model which include internal/external mud cake effects; 3) determining drilling safe mud weight window based on various failure criteria; 4) identifying troublesome zones with narrow mud weight window throughout the well trajectory; 5) performing an integrated wellbore strengthening analysis based on different mechanisms (e.g., induced fracture propagation and plugging, thermal, external and internal mud cake effects); 6) performing an integrated mud loss volume prediction based on different mechanisms (e.g., natural fracture loss, induced fracture loss, formation loss); and 7) quantifying the amount of strengthening and re-generating mud weight window for safe drilling. The integrated tool provides a suitable workflow when drilling through depleted zones and for lost circulation. 1. INTRODUCTION Lost circulation is one of the major causes of nonproductive time in drilling operations. If the near wellbore stress state dictates that they should, induced fractures initiate and propagate away from the wellbore and fluid is lost into the formation. This is particularly true for wells being drilled in complex geological settings (such as deep water or highly depleted zones/intervals). Several geomechanical mechanisms (e.g., near wellbore fracture propagation, thermo-poroelastic processes, mud cake formation, etc.) can act together to control near wellbore stress field, induced fracture characteristics and associated lost circulation risk. If induced fracture characteristics can be accurately predicted, loss circulation materials can be added to the system to plug fractures of different size(s) and width(s) to increase fracture re-initiation pressure (FRIP). This phenomena is also referred as "wellbore strengthening" in the literature. Induced fracture characteristics are predominantly controlled by the near wellbore stress field. Therefore, one of the prerequisites for a successful design is to establish a workflow (that integrates multiple mechanisms within the framework of a geomechanical engine) to calculate a realistic stress field around the wellbore, to asses induced fracture risk and to come up with an effective wellbore strengthening strategy.
- Research Report > Experimental Study (0.48)
- Research Report > New Finding (0.47)
Use of Drilling With Liner Technology to Mitigate a Catastrophic Loss Interval – A Successful Case Study in the North Sea
van-Aerssen, Mark (Wintershall Noordzee B.V.) | Rosenberg, Steven M. (Weatherford) | Wever, Ronald (Weatherford) | Tan, Ming Zo (Weatherford) | Salinas, Alexandro (Weatherford) | Karimi, Moji (Weatherford) | Winchell, Rex L. (Weatherford)
Abstract The North Sea presents major challenges to drilling and casing installation operations. Drilling a well through the overpressured Scruff Shale and Fan Carbonates in a single hole interval is extremely challenging because the Fan Carbonates have been depleted through production leading to wellbore stability risks due to severe fluid losses. After three unsuccessful attempts using conventional drilling methods resulted in two sidetracks and a well suspension, the North Sea operator looked for alternative means to satisfy the intended well construction objectives. Drilling with Liner (DwL) technology was identified as the most appropriate technique for installation of the planned 9-5/8 in. x 11-3/4 in. liner because: Documented lost circulation problems have been minimized or eliminated through prior use of liner drilling technology. The hazard interval can be isolated with a single trip using a PDC-drillable casing bit without sacrificing hole size. Liner systems deployed for DwL provide for high torsional capability as well as resistance to projected cyclic fatigue stresses over the projected DwL interval. DwL BHA stabilization design has been proven to maintain established inclination and azimuth while drilling in liners over hundreds of feet. This paper illustrates the collaborative approach a North Sea operator and international oilfield services company used for the planning and successful execution of a 9-5/8 in. x 11-3/4 in. drilling with liner (DwL) operation to drill through the over pressured Scruff Shale, landing the liner in the depleted Fan Carbonates in a single hole section. Early partnering with the service company led the operator to implement DwL technology to meet established well construction objectives. Since DwL technology encompasses a multitude of engineering disciplines, these would be integrated into the drilling plan in a seamless manner, ensuring the DwL objectives would be met. Also made evident is how the newly formed operator-service company team was able to react on short notice, facilitating installation of an unplanned solid expandable liner as well as additional liners to address subsequent lost circulation events.
- Europe > United Kingdom > North Sea (1.00)
- Europe > Norway > North Sea (1.00)
- Europe > North Sea (1.00)
- (2 more...)
- Geology > Geological Subdiscipline (0.69)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.57)
- Well Drilling > Pressure Management > Well control (1.00)
- Well Drilling > Drilling Operations > Running and setting casing (1.00)
Abstract The maturation of fields in the Gulf of Mexico shelf means that many future sidetracks and recompletions will require drilling through depleted formations. The difficulty of drilling through such formations is especially high when adjoining zones are over-pressured since the mud weight required to maintain overbalance creates significant risk of differential sticking and lost circulation in the depleted zone. Three dump waterflood wells drilled conventionally in 2012 encountered significant problems while drilling the depleted zones. These included lost returns while cementing, hole pack-off and in one case, differential sticking which required the drill string to be severed and a sidetrack to be performed. The three wells incurred an average of 258 hours of associated NPT, which negatively affected project economics and led the operator to evaluate other drilling methods for such depleted sections. Following a detailed and collaborative planning process between the operator and an integrated service provider, it wasdecided to sidetrack an existing well and use drilling with liner (DwL) method to drill through two depleted sandstone intervals bounded by over-pressured shale zones and cement the liner to facilitate the completion of a dump flood well. There were no observed losses while drilling the entire 577 ft. interval, and also during the cement job with the liner lap testing successfully. An additional benefit was the exceptionally low formation damage observed during the subsequent frac-pack completion as compared to the previous wells. Overall, this operation suggests that DwL is an enabling technology for drilling depleted sands. In this paper the authors will describe the planning process in detail and will continue to describe how drilling with liner technology was successfully implemented to drill a sequence of depleted sands and over-pressured shale formations in a field where conventional drilling had presented many problems.
- North America > United States (0.70)
- North America > Mexico (0.61)
- Europe > Norway > Norwegian Sea (0.24)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.75)
Abstract This paper will illustrate the collaborative approach an international oilfield services company and Gulf of Mexico operator used for the planning and successful execution of a 9-7/8-in. x 14-in. Drilling with Liner (DwL) operation to isolate a 6.5 ppg depleted sand interval and mitigate expected losses in a deep water block of Mississippi Canyon. Conventional methods would have most likely have required an 11-3/4-in. or 11-7/8-in. contingency liner for the operator to meet their well construction objectives. Early collaboration between the service company and operator identified DwL technology as the core technology to meet the operator's well construction objectives. The DwL process allows a hazard interval to be isolated in a single trip resulting in less risk and exposure compared to the use of conventional drilling methods. Since DwL technology encompasses a multitude of engineering disciplines, these were integrated into the drilling plan in a seamless manner, ensuring the DwL objectives would be met. To accomplish this, the service company formed a dedicated well engineering team which collaborated with the operator early on in their well planning process. The engineering disciplines with associated modeling during the DwL planning phase provided technical assurance the 9-7/8″ liner string could be drilled to a satisfactory setting depth while also providing a high-integrity wellbore to the operator over the entire life of the well. These disciplines included: Torque, drag and hydraulics modeling of the liner running and drilling operation, Connection cyclic fatigue analysis, BHA and directional tendency modeling Cementation and centralization Formation drillability analysis Plastering effect evaluation During the planning phase, regular operator-service company communications along with project scheduling software gave the operator assurance that agreed upon deliverables would be completed in the allotted time frame with the intended well objectives met. The 9-7/8-in. x 14-in. liner successfully drilled through the depleted sand reaching a competent setting point, eliminating a potential contingency liner. This paper will present the DwL planning process, associated risk assessment modeling to ensure that safety, environmental and DwL objectives were met, and the DwL operation with its successful outcome
Abstract Drilling depleted reservoirs is often encountered with a host of problems leading to increase in cost and non-productive time. One of these faced by drillers is lost circulation of drilling fluids which can lead to bigger issues such as differential sticking and well control events. Field applications show that wellbore strengthening effectively helps reduce mud loss volume by increasing the safe mud weight window. Wellbore strengthening applications are usually designed based on induced fracture characteristics (i.e., fracture length, fracture width and plug location within fracture). In general, these fracture characteristics depend on several parameters, e.g., in-situ stress magnitude, in-situ stress anisotropy, mechanical properties, rock texture, wellbore geometry, mud weight, wellbore trajectory, pore pressure, natural fractures, formation anisotropy and among others. Analytical models available in the literature oversimplify fracture initiation and propagation process with assumptions such as: isotropic stress field, no near wellbore stress perturbation effects, vertical or horizontal wells only (no deviation/inclination), constant fracture length and constant pressure within the fracture. For more accurate predictions, different numerical methods, i.e., finite element, boundary element, etc., have been utilized to determine fracture width distribution. However these calculations can be computationally costly or hard to implement in near real time. The aim of this study is to provide a fast running, semi-analytical workflow to accurately predict fracture width distribution and fracture re-initiation pressure (FRIP). The algorithm and workflow can account for near wellbore stress perturbations, far field stress anisotropy, and wellbore inclination/deviation. The semi-analytical algorithm is based on singular integral formulation of stress field and solved using Gauss-Chebyshev polynomials. Proposed model is computationally efficient and accurate. The model also provides a comprehensive perspective on the formation strengthening scenarios; a tool for improved LCM design and how they are applicable during drilling operation (in particular through depleted zones). Sensitivity analysis included in this paper quantifies the effect of different rock property, in-situ stress field/anisotropy and wellbore geometry/deviation on the fracture width distribution and FRIP. Additionally, the case study presented in this paper demonstrates the applicability of the proposed workflow in the field.
- North America > United States > Texas (0.28)
- North America > United States > California > San Francisco County > San Francisco (0.28)
Abstract Lost circulation has plagued the industry since the beginning of drilling. Historically, severity of losses has been categorized based on the amount of barrels lost to the formation, i.e., seepage, partial, and total. Though helpful, this strategy doesn't help understand the underlying drive mechanism(s) for losses and doesn't provide enough data to propose a solution. The recently adopted category is focused on the lost-circulation mechanism based on the properties of the exposed formation; these classifications are losses to 1) pore throats, 2) induced or natural fractures, and 3) vugs or caverns. This study provides an integrated workflow to predict expected losses for such classification/mechanism of losses. Mud loss through fracturing is categorized based on fracture types, i.e., natural or induced fractures. Different models are used with respect to the fluid-loss mechanism in natural and induced fractures. These models take into account the effect of fracture breathing. In addition, mud loss through the pores on the wellbore and the fracture face is modeled based on formation and mud-cake filtration properties, coupled with the fracture losses. Losses through induced fractures generally occur when ECD exceeds fracture gradient. This happens due to erroneous prediction of the mud weight window, lack of the key information, harsh downhole pressure/temperature and some other operational factors. A field case from deep water Gulf of Mexico is presented in this paper showing how an inaccurate mud window can yield in drastic mud losses. In addition, rock properties and field in-situ stress govern fracture width and fracture propagation. Losses to vugs/caverns are usually total losses due to very large openings in the rock; recommendations are provided on how to control severe losses. Lost circulation not only causes the adverse effect of mud loss itself; it can also lead to several other issues, such as formation damage, stuck pipe, hole collapse, and well-control incidents. The current industry trend is moving towards drilling more low-pressure zones, and lost-circulation planning is becoming a vital part of these projects. Knowledge of the type and the expected amount of mud loss can help engineers select the most appropriate and effective solution and preplan accordingly. This information also provides criteria to evaluate the effectiveness of the applied lost-circulation strategy. In this study we review LCM treatments, wellbore strengthening, MPD, and CwD as some of the most common remedial techniques.
- Europe (0.94)
- Asia > Middle East > UAE (0.29)
- North America > United States > Texas (0.28)
- North America > United States > Louisiana (0.28)
- Research Report > New Finding (0.34)
- Overview (0.34)
Abstract Drill cuttings have always been used to gather data from subsurface formations. Since the onset of the drilling industry, mud loggers have used cuttings to plot the lithology column. Reservoir drill cuttings have also been used to further understand formation properties, such as porosity and permeability. In addition, cuttings have been the subject of waste management research for years. Cuttings analysis is an important aspect of real-time drilling operations and the correct sampling, measurement, and interpretation of cuttings help prevent problems and improve drilling performance. The first part of this study describes the sampling and measurement of drill cuttings, while the second examines data interpretation. Historically, cuttings analysis has been done by the solid control crew to enhance solids-removal efficiency and by mud loggers to obtain subsurface data. Although these two groups communicate their analyses with the drilling engineer, current visual inspection and sampling procedures provide information that is potentially unreliable for real-time drilling decisions. Cuttings affect drilling fluid properties, annular-pressure losses, hole cleaning, wellbore stability/integrity, penetration rate and many other drilling considerations. Cuttings properties such as particle-size distribution, volume, shape, etc., can reveal the start of a drilling problem or offer justifications for decisions to improve performance. Reliable measures must be in place for taking accurate samples and reporting related properties to enable the drilling engineer to make meaningful correlations. This study intends to provide guidelines on sampling and measurement methodology for the benefit of drilling engineers. With recent advancements and the introduction of real-time particle-size distribution and Coriolis in-line flowmeters, new data sources are available. These tools provide plenty of valuable information, but decisions need to be made about where, when, and how to take samples for reliable output data. Particles mixed with cuttings that are not generated by bit action, e.g., cavings and mud additives, also need to be accounted for and differentiated while sampling and measuring cuttings. There are correlations between drilling problems and cuttings properties; however, if detected early, these problems can be prevented to enhance drilling performance. Early detection is contingent upon a reliable sampling method, which represents the annular cuttings, interacting with the formation. Thus, a procedure is proposed for proper sampling and measurement of cuttings.
- Europe (0.68)
- North America > United States > Texas (0.28)
- Well Drilling > Drilling Operations (1.00)
- Well Drilling > Drilling Measurement, Data Acquisition and Automation > Mud logging / surface measurements (1.00)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (1.00)
- Well Drilling > Drilling Fluids and Materials > Cuttings transport (1.00)
Abstract Casing Drilling is an innovative drilling method wherein the well is drilled and cased simultaneously. The small annulus of Casing Drilling can create a controllable dynamic ECD (Equivalent Circulating Density). Casing Drilling technology permits the same desired ECD as conventional drilling to be achieved using a lower, but optimized, flow rate, rheological properties, and mud weight. In this paper, the frictional pressure loss during Casing Drilling operation is evaluated using Computational Fluid Dynamics. Annular pressure losses have received substantial attention in theoretical analyses, laboratory assessment and actual well measurements. Combinations of casing motion, annular eccentricities, wall roughness and fluid temperatures along the length of the annulus affect fluid flow regimes that control annular pressure losses. Current analytical solutions have limited applicability for complex conditions with pipe rotation and eccentricity. In this study, the pressure losses during Casing Drilling operation are investigated using computational fluid dynamics. The results are compared against the available analytical solution and field data. The effect of pipe rotation and eccentricity on the frictional pressure loss is investigated as well. According to the simulation results, the pipe rotation reduces the frictional pressure loss for Yield-Power-law fluid which would be beneficiary during the casing drilling operation. It is found that the pipe eccentricity has a significant effect on the ECD calculation. The industry is moving towards more challenging jobs in narrow pressure window scenarios such as deep-water and HPHT applications. Drilling with casing/liner is among the primary options to complete these sections due to strengthening effects associated with plastering the wellbore wall and also eliminating conventional drill pipe trip. Having accurate models for ECD including the effects of pipe rotation and eccentricity in the narrow annulus is essential to the success of these challenging jobs.
- North America > United States > Texas (1.00)
- Asia > Middle East (1.00)
- Europe (0.69)
- South America (0.68)
- South America > Peru > Marañón Basin (0.99)
- North America > United States > Texas > Sabinas - Rio Grande Basin > Lobo Field (0.99)
- North America > United States > New Mexico > San Juan Basin (0.99)
- (4 more...)