Schlumberger (Netherlands)

Schlumberger RPS (Retail Petroleum Systems) integrated the Goal/Question/Metric approach into their existing measurement programs to improve their program performance. Key to their success was the use of feedback sessions as a forum to analyze and interpret measurement data. The paper discusses the elements of the GQM approach and fitting GQM to a measurement program.

This study aims to describe the intensity and load demands of different stage types within a cycling Grand Tour. Nine professional cyclists, whom are all part of the same World-Tour professional cycling team, participated in this investigation. Competition data were collected during the 2016 Giro d'Italia. Stages within the Grand Tour were classified into four categories: flat stages (FLAT), semi-mountainous stages (SMT), mountain stages (MT) and individual time trials (TT). Exercise intensity, measured with different heart rate and power output based variables, was highest in the TT compared to other stage types. During TT's the main proportion of time was spent at the high-intensity zone, whilst the main proportion of time was spent at low intensity for the mass start stage types (FLAT, SMT, MT). Exercise load, quantified using Training Stress Score and Training Impulse, was highest in the mass start stage types with exercise load being highest in MT (329, 359 AU) followed by SMT (280, 311 AU) and FLAT (217, 298 AU). Substantial between-stage type differences were observed in maximal mean power outputs over different durations. FLAT and SMT were characterised by higher short-duration maximal power outputs (5-30 s for FLAT, 30 s-2 min for SMT) whilst TT and MT are characterised by high longer duration maximal power outputs (>10 min). The results of this study contribute to the growing body of evidence on the physical demands of stage types within a cycling Grand Tour.

The aggregation and deposition of colloidal asphaltene in reservoir rock is a significant problem in the oil industry. To obtain a fundamental understanding of this phenomenon, we have studied the deposition and aggregation of colloidal asphaltene in capillary flow by experiment and simulation. For the simulation, we have used the stochastic rotation dynamics (SRD) method, in which the solvent hydrodynamic emerges from the collisions between the solvent particles, while the Brownian motion emerges naturally from the interactions between the colloidal asphaltene particles and the solvent. The asphaltene colloids interact through a screened Coulomb potential. We vary the well depth ϵcc and the flow rate v to obtain Peflow >> 1 (hydrodynamic interactions dominate) and Re << 1 (Stokes flow). In the simulations, we impose a pressure drop over the capillary length and measure the corresponding solvent flow rate. We observe that the transient solvent flow rate decreases when the asphaltene particles become more “sticky”. For a well depth ϵcc = 2kBT, a monolayer deposits on the capillary wall. With an increasing well depth, the capillary becomes totally blocked. The clogging is transient for ϵcc = 5kBT, but appears to be permanent for ϵcc = 10–20kBT. We compare our simulation results with flow experiments in glass capillaries, where we use extracted asphaltenes in toluene, reprecipitated with n-heptane. In the experiments, the dynamics of asphaltene precipitation and deposition were monitored in a slot capillary using optical microscopy under flow conditions similar to those used in the simulation. Maintaining a constant flow rate of 5 µL min−1, we found that the pressure drop across the capillary first increased slowly, followed by a sharp increase, corresponding to a complete local blockage of the capillary. Doubling the flow rate to 10 µL min−1, we observe that the initial deposition occurs faster but the deposits are subsequently entrained by the flow. We calculate the change in the dimensionless permeability as a function of time for both experiment and simulation. By matching the experimental and simulation results, we obtain information about (1) the interaction potential well depth for the particular asphaltenes used in the experiments and (2) the flow conditions associated with the asphaltene deposition process.

Abstract This paper describes a new method based on the analysis of non-steady state wellbore temperature distributions impacted by geothermal temperature profile, Joule-Thomson and adiabatic effects in reservoir flow to describe near wellbore parameters such as permeability distribution and to estimate flow rate distribution between producing layers. The solution of the inverse problem with respect to parameters of near wellbore zone is based on the quantitative analysis of the transient baro-thermal effects resulting from the single-phase fluid flow from the reservoir into the wellbore. In the steady state case the reservoir thermal effect is the same as the throttling (Joule-Thomson) one. It is reduced to the adiabatic effect while the fluid is stagnant. In the general case for non-steady state flow the change of reservoir fluid temperature is a combination of frictional heating and cooling resulting from the expansion of the fluid. Non-isothermal well testing (NIT) relies on the analysis of these fluid temperature changes. The method discussed in this paper allows evaluating parameters of near wellbore region (permeability and radius of damaged zone) and could be complimentary to the conventional well testing practices for a single-layer reservoir and to estimate flow rate distribution among the pay zones in a multi-layer case (zonal allocation). The paper develops mathematical models and presents the results of numerical simulation for transient processes after the start of the production phase and during well test operations including multi-rate testing. Limited to the particular cases of unsteady processes after specific wellbore operations (changes of production regimes and shut-ins), the transient analytical solutions assume that the fluid may be considered incompressible and that no conductive heat transfer occurs. In order to take into account compressibility and thermal conductivity, detailed numerical modeling has been performed. The paper compares the numerical results to experimental data and shows that the fluid heat capacity in wellbore perforated zone must be considered for appropriate interpretation of initial bottomhole temperature change versus time, in particular for small rates. Based on the analysis of the simulation results, an inverse model solution for the estimation of the near wellbore zone parameters from reservoir fluid temperature and wellbore pressure transients is proposed. The method comprises first-order estimation from analytical solution and their further numerical refinements by non-linear regression for the system "reservoir-wellbore". Example of interpretation of non-isothermal well testing field data is presented demonstrating the usefulness of this new methodology.

An asymptotic model of a hydraulic-fracture flow of a sedimenting concentrated suspension is formulated on the basis of the two-fluid approach with account of transverse particle migration. In the thin-layer approximation, a two-dimensional system of equations averaged across the fracture is constructed with account for a nonuniform distribution of the particle concentration. As compared to the similar model without particle migration, the averaged two-dimensional equations contain modified coefficients which explicitly depend on the width of the flow core occupied by the particles. Using the model constructed, a numerical simulation is performed, which shows that the particle migration towards the fracture center results in the increase in the depth of particle penetration into the fracture and the suppression of gravitational convection in the vicinity of the leading front. The calculations are compared with available experimental data and an analytical formula for the height of the dense packed sediment. A good agreement between the analytical theory, the experiments, and the two-dimensional calculations is attained.

Many success stories have been reported on specific effects of measurement, but little is known about the multiple interactions of measurement programmes with the business environment of a software organisation. This paper summarises industrial experiences with the Goal/Question/Metric (GQM) approach to software engineering measurement. They are based on long-term observation and additional detailed investigations at Schlumberger RPS. The paper reports the business impact of GQM in terms of identified benefit, cost models, and factors for successful application of GQM.

ABSTRACT This paper describes the measurements of the acoustic and petrophysical properties of two suites of low‐shale sandstone samples from North Sea hydrocarbon reservoirs, under simulated reservoir conditions. The acoustic velocities and quality factors of the samples, saturated with different pore fluids (brine, dead oil and kerosene), were measured at a frequency of about 0.8 MHz and over a range of pressures from 5 MPa to 40 MPa. The compressional‐wave velocity is strongly correlated with the shear‐wave velocity in this suite of rocks. The ratio V P / V S varies significantly with change of both pore‐fluid type and differential pressure, confirming the usefulness of this parameter for seismic monitoring of producing reservoirs. The results of quality factor measurements were compared with predictions from Biot‐flow and squirt‐flow loss mechanisms. The results suggested that the dominating loss in these samples is due to squirt‐flow of fluid between the pores of various geometries. The contribution of the Biot‐flow loss mechanism to the total loss is negligible. The compressional‐wave quality factor was shown to be inversely correlated with rock permeability, suggesting the possibility of using attenuation as a permeability indicator tool in low‐shale, high‐porosity sandstone reservoirs.

Seismic reflection data can be redatumed to a specified boundary in the subsurface by solving an inverse (or multidimensional deconvolution) problem. The redatumed data can be interpreted as an extended image of the subsurface at the redatuming boundary, depending on the subsurface offset and time. We retrieve target-enclosed extended images by using two redatuming boundaries, which are selected above and below a specified target volume. As input, we require the upgoing and downgoing wavefields at both redatuming boundaries due to impulsive sources at the earth’s surface. These wavefields can be obtained from actual measurements in the subsurface, they can be numerically modeled, or they can be retrieved by solving a multidimensional Marchenko equation. As output, we retrieved virtual reflection and transmission responses as if sources and receivers were located at the two target-enclosing boundaries. These data contain all orders of reflections inside the target volume but exclude all interactions with the part of the medium outside this volume. The retrieved reflection responses can be used to image the target volume from above or from below. We found that the images from above and below are similar (given that the Marchenko equation is used for wavefield retrieval). If a model with sharp boundaries in the target volume is available, the redatumed data can also be used for two-sided imaging, where the retrieved reflection and transmission responses are exploited. Because multiple reflections are used by this strategy, seismic resolution can be improved significantly. Because target-enclosed extended images are independent on the part of the medium outside the target volume, our methodology is also beneficial to reduce the computational burden of localized inversion, which can now be applied inside the target volume only, without suffering from interactions with other parts of the medium.

ABSTRACT We studied the electric response of fractures with laboratory experiments and numerical simulations for a full-bore formation microimaging tool. The laboratory setup was designed and built to perform controlled experiments with accurate measurements of all principal properties involved for electric borehole imaging. These properties are formation resistivity, mud resistivity, fracture aperture, pad position, and button current. The experiments were conducted on two types of limestone for fracture apertures ranging from 0.1 to 0.9 mm and mud/formation resistivity contrasts varying from 1/100 to 1/10,000. A numerical model was used to reproduce the laboratory configuration and to validate the results. The model proved to be an effective tool to optimize the experimental setup, and it was also used to study the effect of standoff (up to 5 mm) on the measured integrated additional current. Linear relationships between the fracture aperture and measured integrated current were found to be valid for the laboratory experiment and the corresponding numerical simulation. The measured integrated current could therefore be used to determine the fracture aperture if the other parameters are known. Two coefficients in the relationship were found to differ from those previously found using numerical simulations for the actual borehole situation. These differences are attributed to tool- and scale-dependent factors.

Resolving details in subsurface reservoir parameters from surface waveform data is a challenging problem, particularly when a reservoir is beneath a complex overburden whose properties are also poorly known. We have developed new metrics for detecting and quantifying errors in subsurface models that are well-suited for target-oriented inversion. Our metric, when combined with state-of-the art redatuming, aims at enabling waveform inversion for target volume parameters with no need to resolve model features elsewhere (e.g., in the overburden). We refer to these metrics as “interferometric objective functions” because they rely on extrapolation from reciprocity integrals commonly used in seismic interferometry. As in seismic interferometry, wavefield extrapolation retrieves the wave response between two points by combining observed data with an extrapolator that describes the response between the subsurface and the data boundary. When the source point is outside a target volume, either forward time or reverse time extrapolation produces the same field. However, because they physically rely on different components from the boundary data, the forward time and reverse time extrapolated fields are only equal when the model used is consistent with the real subsurface within the target volume. As such, we use the difference between the forward time and reverse time extrapolated fields to define subsurface-domain metrics that quantify model errors. Our approach thus provides a new metric for target-oriented nonlinear inversion in the subsurface domain, one that fundamentally differs from other subsurface domain metrics based on, e.g., focusing or image extensions.

In ESPRIT project PROFES, measurement according to the Goal/Question/Metric (GQM) approach is conducted in industrial software projects at Drager Medical Technology, Ericsson Finland, and Schlumberger Retail Petroleum Systems. A comparative case study investigates three different ways of applying GQM in product-focused process improvement: long-term GQM measurement programmes at the application sites to better understand and improve software products and processes; GQM-based construction and validation of product/process dependency models, which describe the process impact on software quality; and cost/benefit investigation of the PROFES improvement methodology using GQM for (meta-) analysis of improvement programmes. This paper outlines how GQM is applied for these three purposes.

OBJECTIVE: Functional constipation (FC) has a major impact on the health-related quality of life (HRQoL) of children. The aim of this study was to evaluate parent-child agreement on HRQoL in children (8-17 years) with FC in primary care. METHODS: Children diagnosed with FC by their clinician were eligible. HRQoL was measured with the Defecation Disorder List (DDL, score 0-100), and the EuroQol-5-Dimension-Youth Visual Analogue Scale (EQ-5D-Y-VAS, scale 0-100). Parent-child agreement was examined with discrepancy scores, intraclass correlation coefficients and Bland-Altman plots. RESULTS: Fifty-six children, median age of 10 years (IQR 8-12) and their parents were included. Parent-child agreement at a group level was good, with an intraclass correlation coefficient of 0.80 (95% confidence interval 0.67 to 0.88) for the DDL, and 0.78 (95% confidence interval 0.65 to 0.87) for the EQ-5D-Y-VAS. Mean discrepancy scores for the DDL and EQ-5D-Y-VAS were small: -2.6 and -2.9, implying that parents were slightly more positive about the HRQoL than their children. Bland-Altman plots showed considerable discordance between individual parent-child pairs. Limits of agreement were -19.7 and 14.6 for the DDL and -27.6 and 21.8 for the EQ-5D-Y-VAS. CONCLUSIONS: There is good parent-child agreement on HRQoL in children with FC at group level. However, a substantial number of parent-child pairs differed considerably on their rating of the HRQoL of the child. Therefore, we recommend clinicians, if they want to have an impression of the impact of the FC on the HRQoL of the child, to ask both the child and the parent(s).

The linear hydrodynamic stability of dusty-gas flow in a boundary layer on a flat plate is considered in the framework of a two-fluid model. The phase interaction is described by the Stokes and Saffman forces. The particle volume fraction is negligibly small, but the feedback effect on the carrier phase is taken into account due to the finiteness of the dispersed-phase mass concentration. In the main flow, the phase velocities coincide and the particles are distributed non-uniformly, namely, in the form of a localized dust layer. The equations of two-phase flow, linearized with respect to small three-dimensional disturbances, are reduced to five differential equations for the disturbance amplitudes of the normal components of the carrier-phase velocity and vorticity and three velocity components of the dispersed phase. In the framework of the classical (modal) approach, the analysis of two-dimensional disturbances is performed and the dependence of the critical Reynolds number on the dimensionless parameters is found. It is shown that the flow is most stable when the maximum of the particle concentration is located in the vicinity of the so-called “critical layer”. The analysis of non-modal (algebraic) instability demonstrated that the maximal kinetic energy of the optimal disturbances is attained when the narrow dust layer is located in the vicinity of the displacement thickness of the boundary layer.

ABSTRACT We study the mechanical deformation of fractures under normal stress, via tangent and specific fracture stiffnesses, for different length scales using numerical simulations and analytical insights. First, we revisit an equivalent elastic layer model that leads to two expressions: the tangent stiffness is the sum of an “intrinsic” stiffness and the normal stress, and the specific stiffness is the tangent stiffness divided by the fracture aperture at current stress. Second, we simulate the deformation of rough fractures using a boundary element method where fracture surfaces represented by elastic asperities on an elastic half‐space follow a self‐affine distribution. A large number of statistically identical “parent” fractures are generated, from which sub‐fractures of smaller dimensions are extracted. The self‐affine distribution implies that the stress‐free fracture aperture increases with fracture length with a power law in agreement with the chosen Hurst exponent. All simulated fractures exhibit an increase in the specific stiffness with stress and an average decrease with increase in length consistent with field observations. The simulated specific and tangent stiffnesses are well described by the equivalent layer model provided the “intrinsic” stiffness slightly decreases with fracture length following a power law. By combining numerical simulations and the analytical model, the effect of scale and stress on fracture stiffness measures can be easily separated using the concept of “intrinsic” stiffness. We learn that the primary reason for the variability in specific stiffness with length comes from the fact that the typical aperture of the self‐affine fractures itself scales with the length of the fractures.

ABSTRACT We revisit an exact, quasi-static, semianalytical solution for the effective tube-wave modulus for any borehole orientation relative to an anisotropic medium of arbitrary symmetry and strength. This exact solution agrees very well with the one computed from a finite-element model (FEM). We compare the exact solution with several analytical approximations for well deviations from vertical to horizontal and for different transversely isotropic media. For elliptic media, we show that the Rice and Chi-Tang approximations are in accordance with the exact solution because they depend only on the horizontal and vertical shear-wave velocity. For anelliptic media, we show that the maximum difference between the exact solution and the Norris-Sinha or Chi-Tang perturbation approximation becomes increasingly significant with increasing degree of anellipticity and shear-wave anisotropy with a maximum error of 5%, 10%, and 18% for Thomsen parameters less than 0.25, 0.4, and 0.6, respectively.

Abstract Oil field chemicals are incorporated into a fluid design to solve a specific technical wellbore or matrix problem in a well, such as stimulation; water, sand, and scale control; or damage removal. By their chemistry, some chemicals have primary active ingredients that may be harmful if discharged to the environment. Improving the characteristics of these chemical products to marine life requires changes in previously acceptable products, such as elimination of restricted chemicals as well as incorporating chemical components with reduced ecotoxicity. Additional chemical alternatives should be provided to reduce the potential effects of the total chemical/fluid system. This paper focuses on the last four years of an aggressive product development for acid corrosion inhibition and application. Product improvements were achieved by eliminating restricted chemicals, decreasing product toxicity, and improving biodegradability. The aim of the paper is to demonstrate that for a complete solution, chemical reformulation and development of new chemistry must be considered hand in hand with improved operational practices to provide a maximum overall risk reduction. This paper recognizes that regulation of the use of hazardous chemicals offshore for oilfield stimulation and completion applications is one method for protecting the marine environment; however, for the long term, aggressive technical chemical improvements must continue. Development of more environmentally acceptable products does not arbitrarily mean that products are less efficient and less cost effective. More efficient products with improved ecotoxicity performance have been developed. Chemical replacement schemes are important but may be limited in what they can ultimately achieve. More important are process management and the more efficient use of chemicals with the goal of no waste.

We introduce a new technique that uses multicomponent seismic measurements that would be recorded by a true multicomponent streamer to reconstruct the seismic wavefield at any desired position between streamers. This method, called Multichannel Interpolation by Matching Pursuit (MIMAP), operates on pressure and crossline particle motion measurements. As a data‐dependent technique, MIMAP can interpolate severely aliased data without any assumptions about seismic events such as linearity or the model related to the seismic wavefield. MIMAP has the capability to perform well in the presence of irregular sampling and is robust even when only a small number of samples are available.

Abstract A significant share of gas production in the Dutch sector of the southern North Sea Basin comes from Permian Rotliegend fault blocks. Precise knowledge of the positions of these faults is necessary for efficient exploitation of the reservoir structures and for future field development strategies. Two areas are presented where the lateral resolution of the surface seismic data was not sufficient to determine positions of major fault block boundaries accurately. Walkaway borehole seismic profiles were shot over each of these areas with the objective of illuminating the fault boundaries to obtain an image with a higher resolution. The images were generated using borehole seismic reflection-point mapping and migration techniques. Large-aperture migrations tend to produce unacceptable migration smiles, while reflection-point mapping is a model-dependent process. A hybrid approach to these processes was necessary to avoid problems associated with the limited angular illumination permitted by the field acquisition geometries. Reliable images of the fault boundaries were obtained using migration apertures of less than + or -5 degrees relative to the structural dips in the background model and by matching that model with the surface seismic and borehole seismic data. The stability of the process and, therefore, the accuracy of the lateral positioning were verified by testing the migration process using a range of apertures.

Schlumberger RPS successfully applies software measurement to support their software development projects. It is proposed that the success of their measurement practices is mainly based on the organization of the interpretation process. This interpretation of the measurement data by the project team members is performed in so-called 'feedback sessions'. Many researchers identify the feedback process of measurement data as crucial to the success of a quality improvement program. However, few guidelines exist about the organization of feedback sessions. For instance, with what frequency should feedback sessions be held, how much information should be presented in a single session, and what amount of user involvement is advisable? Within the Schlumberger RPS search to improve feedback sessions, the authors explored learning theories to provide guidelines to these type of questions. After all, what is feedback more than learning?.