An Ensemble-Based Solution for Automating Drilling Engineering: Application to Directional Surveying
Abstract: Drilling engineering and drilling operation are two steps of the well construction process that are treated sequentially and separately. The interface between those two steps is the drilling program, i.e., a unique solution that has been singled out and analyzed in detail during well planning. However, when an unexpected situation occurs during the drilling operation, the drilling program is of little use to take informed decisions as it does not contain any information about acceptable tolerances. … Show more
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Cited by 8 publications
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Analysis of the Sources of Uncertainty in Geopressure Estimation While Drilling
Geopressure estimation is an important aspect of well planning and execution. However, there are many sources of uncertainty that can affect the accuracy and timing of the prognosis. These uncertainties are associated with data produced by many different disciplines at various times throughout the life of the well. As subject matter experts tend to work in silos these uncertainties are often unshared, and there is no appropriate routine performance of uncertainty propagation across disciplines. This can negatively affect decision making during both the engineering and operational phases of a well. Uncertainty requirements across disciplines are often not formulated into coherent uncertainty management. It is therefore important to understand the possible sources of uncertainty to better quantify the estimation of geopressures and to make smarter decisions. This paper describes the uncertainties associated with each estimate of geopressure, their locations in the multi-discipline silos, and the current relationship between estimates. With this comes the realization of a structure or method for combining the individual uncertainties to provide a clearer idea of geopressure estimation and its inherent uncertainty. For instance, combining wellbore position uncertainty with the stratigraphic earth model uncertainty makes possible the estimation of the spatial probability distribution of particular geopressure related observations. The sources of information for geopressure prognosis are many, spread across disparate systems with various discipline ownership. Even direct and real-time observations of formation fluid influx, borehole collapse or formation fracturing can depend on the precision of downhole pressure measurements and knowledge. Extrapolate measured downhole pressures to positions far removed from the measurement point is often necessary. This requires accurate calculation of hydrostatic and hydrodynamic pressures and the wellbore and vertical depth positions to infer pressure profiles along the borehole. These profiles are a function of the accuracy of characterization of the pressure and temperature behavior of the drilling fluid properties and the well depth. Temperature estimations depend on definition of geothermal gradients and the precision of heat transfer calculations causing a varying degree of accuracy for baseline profiles to base operational decision. It is possible to measure pore pressures in situ, or to estimate them using trend analysis of formation evaluation or drilling logs. Factors influencing the precision of the results include the actual measurement depth value uncertainty, and the impact of wellbore position uncertainty on their correlation with an earth model. Leak-off tests deliver information about geopressure margins, but the interpretation of flow-back measurements creates further uncertainties that propagate across the prognosis. The propagated uncertainties from all these sources can be derived using stochastic simulations, yielding, when combined, a quantitative assessment of geopressures. In addition, Kriging methods can incorporate new geopressure estimations in a geomechanics oriented earth model. The paper provides a list of possible sources of uncertainties and a possible categorization of their origins. It describes the causal links between the sources of uncertainties and their effect on the quality of geopressure prognosis. The purpose is to facilitate the adoption of quantitative uncertainty assessment methods by the well construction community for geopressure estimations.
Analysis of the Sources of Uncertainty in Geopressure Estimation While Drilling
Geopressure estimation is an important aspect of well planning and execution. However, there are many sources of uncertainty that can affect the accuracy and timing of the prognosis. These uncertainties are associated with data produced by many different disciplines at various times throughout the life of the well. As subject matter experts tend to work in silos these uncertainties are often unshared, and there is no appropriate routine performance of uncertainty propagation across disciplines. This can negatively affect decision making during both the engineering and operational phases of a well. Uncertainty requirements across disciplines are often not formulated into coherent uncertainty management. It is therefore important to understand the possible sources of uncertainty to better quantify the estimation of geopressures and to make smarter decisions. This paper describes the uncertainties associated with each estimate of geopressure, their locations in the multi-discipline silos, and the current relationship between estimates. With this comes the realization of a structure or method for combining the individual uncertainties to provide a clearer idea of geopressure estimation and its inherent uncertainty. For instance, combining wellbore position uncertainty with the stratigraphic earth model uncertainty makes possible the estimation of the spatial probability distribution of particular geopressure related observations. The sources of information for geopressure prognosis are many, spread across disparate systems with various discipline ownership. Even direct and real-time observations of formation fluid influx, borehole collapse or formation fracturing can depend on the precision of downhole pressure measurements and knowledge. Extrapolate measured downhole pressures to positions far removed from the measurement point is often necessary. This requires accurate calculation of hydrostatic and hydrodynamic pressures and the wellbore and vertical depth positions to infer pressure profiles along the borehole. These profiles are a function of the accuracy of characterization of the pressure and temperature behavior of the drilling fluid properties and the well depth. Temperature estimations depend on definition of geothermal gradients and the precision of heat transfer calculations causing a varying degree of accuracy for baseline profiles to base operational decision. It is possible to measure pore pressures in situ, or to estimate them using trend analysis of formation evaluation or drilling logs. Factors influencing the precision of the results include the actual measurement depth value uncertainty, and the impact of wellbore position uncertainty on their correlation with an earth model. Leak-off tests deliver information about geopressure margins, but the interpretation of flow-back measurements creates further uncertainties that propagate across the prognosis. The propagated uncertainties from all these sources can be derived using stochastic simulations, yielding, when combined, a quantitative assessment of geopressures. In addition, Kriging methods can incorporate new geopressure estimations in a geomechanics oriented earth model. The paper provides a list of possible sources of uncertainties and a possible categorization of their origins. It describes the causal links between the sources of uncertainties and their effect on the quality of geopressure prognosis. The purpose is to facilitate the adoption of quantitative uncertainty assessment methods by the well construction community for geopressure estimations.
A New Paradigm for Automatic Well Path Generation Using Multidisciplinary Constraints
The well planning process involves many disciplines. Due to the multidisciplinary nature of the process, many iterations are necessary to generate a well path. This is a time-consuming process that finally leads to chosen planned trajectories that may be sub-optimal. It is proposed to radically revise the well path generation process to reach the vision of planning a well in one day with high quality. Departing from the traditional incremental approach to well path generation, the proposed method relies on the collection of experienced-based constraints from each discipline to generate possible alternatives to the well path. A fundamental difference with the classical well path generation process, which works with one or a handful of planned trajectories, is that an ensemble of possible well paths is generated through the proposed method. If the constraints are loose, many planned trajectories might be generated but if the constraints are tight, there may be very few or possibly no solutions. As a result of this new work process, the multidisciplinary team can focus on the relevance of the constraints rather than on the details of the planned trajectory. Capturing these constraints is the fundamental result of the well planning process; the ensemble of possible well paths being only a byproduct of it. The novel method comes with a set of concepts that provide subject matter experts with greater leeway for defining the well path generation problem in a generic way. These concepts have been designed to seamlessly allow for any subsequent updates of the well plan, whether for the target or group of targets and their associated wellbores, the wellbore architecture and its relation to geo-pressure margins, or the surveying program with regards to wellbore position uncertainty. Whenever possible, characteristics attached to these concepts are described implicitly to cope with mutual interactions between constraints. An extensible classification of the constraints is provided and illustrated with examples commonly used to define drilling programs. As a result of the propagation of user-chosen constraints, complex problems such as finding well paths that respect anti-collision criteria, avoid faults or cross them with a high incidence angle if unavoidable, and satisfy inclination limits to cross certain formation layers are solved completely automatically. Innovation does not come for free: the new paradigm presented in this paper induces a significant transformation of the well planning process. However, the versatility of the approach should largely compensate for the expected change in end-users’ habits both by a faster delivery time of every well plan (or even large-scale field development) and by allowing a seamless update of the latter when drilling operations demand it.
Active Magnetic Ranging While Drilling: Prototype Tool Test
A well intercept operation has the scope to drill into an existing well. Similarly, some infill drilling operations are conducted with the scope of avoiding interception with other wells. A prototype of a tool for Active Magnetic Ranging While Drilling (AMR) without the use of a wireline operation has been developed. The main scope of the current article is presenting the results of a prototype test of this new tool in attest well. The ranging tool emits a low frequency alternating current into the formation to reach the target well, and then run through that's casing back to the well being drilled. This electric current set up a variable magnetic field that is measured by the AMR tool determining the direction towards the target well as well as the distance. If drilling a relief well, 10 - 25 wireline runs are needed before the target well is intercepted. The present AMR tool is fully integrated in the drill pipe and, thus, all the tripping operations are avoided. A prototype of an active magnetic ranging tool on the drill pipe has been developed. This tool is outlined in detail in the paper. Most focus will be given to a performance test conducted in a research well in Norway. A drill pipe is placed in a vertical well, being the target well. The AMR tool was run in the research well and the direction and distance to nearby target wells was measured. The set-up and the results of this logging operation conducted on a drill pipe is described in detail. It is shown how the direction and distance between the two wells are measured using the tool. Most intercept operations are not relief well drilling, but cases where a well needs to be intercepted because a well section shall be connected to another well, or during plug and abandonment operation. The tool can also be used for avoiding collision with other wells, which is a relevant scope for drilling infill wells in older fields or radiator wells in geothermal drilling. The tool and its potential are outlined in the paper.
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