Changes In Injection Rate Research Articles

Particle deposition and clogging as an Obstacle and Opportunity for sustainable energy

Fine particle motions have significant implications in porous media, manifesting in various natural phenomena and industrial applications. The movement of particles can lead to channel blockage, resulting in clogging. Depending on the context, clogging can be either advantageous or detrimental. At the scale of fine particles, physiochemical interactions play a crucial role in the clogging process. To examine the influence of these interactions, we have coupled the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory into the Computational Fluid Dynamic-Discrete Element (CFD-DEM) approach. Aside from the physical properties of the fracture systems and the characteristics of fine particles, the injection rate also plays a pivotal role in clogging occurrence. Consequently, we investigated 10 different injection rates and modeled 20 simulation setups with identical particle insertion rates to concurrently analyze the effects of the DLVO theory and injection rate. Our study focused on examining the impact of these parameters on particle behavior in various regions of the domain, including particle-particle force, fluid-particle force, transitional velocity, rotational velocity, fluid velocity, and fluid-particle momentum exchange. Our findings reveal that the DLVO force significantly influences fluid and particle characteristics within the throat blockage. Our results indicated that DLVO consideration increased the particle concentrations by more than 40% before the throat. Moreover, our results demonstrate a transition between different injection rates, where a slight change in injection rate (i.e., 0.06μm/s) can change the system's behavior. We identified a critical fluid injection rate, whereby injecting fluid into the system at a rate surpassing the critical velocity can prevent clogging, while lower rates result in clogging occurrence.

Association Between Injection and Microseismicity in Geothermal Fields With Multiple Wells: Data‐Driven Modeling of Rotokawa, New Zealand, and Húsmúli, Iceland

AbstractUnderstanding injection‐induced microseismicity in geothermal systems can provide insight into reservoir connectedness. However, fault and reservoir complexity are difficult to represent in simple analytical models, which makes it difficult to discern clear relationships from incidental associations. Here, we have used data‐driven models to study how fluid injection and microseismicity are related in the Rotokawa (New Zealand) and Hellisheiði (Iceland) geothermal fields. We tested two classes of model: (a) lagged linear regression of seismicity rate as a function of well injection rates; and (b) systematic extraction of injection time series features that are then evaluated for associations with the seismicity. These models allowed us to determine which wells had the greatest correlation with microseismicity and to explain this association in a reservoir context. Finally, exploring different data types and transformations, we were unable to establish a link between rapid changes in injection rate and seismicity spikes, as suggested by some theoretical models.

Improving the spatial control of soil biocementation using indigenous microorganisms: Column experiments and reactive transport modeling

Microbially-Induced Calcite Precipitation (MICP), or biocementation, is a biomediated soil improvement process that uses microbial ureolytic activity to enable the precipitation of CaCO3 on soil particle surfaces and contacts. As the technology advances towards practical adoption, approaches that can modulate the spatial uniformity of biocementation and maximize treatment extent will be critical towards reducing implementation costs and impacts. In this study, treatment strategies capable of enriching indigenous ureolytic microorganisms at controlled ureolytic activities and the effects of these techniques on resulting spatial distributions of MICP were explored using centimeter- and meter-scale soil column experiments and reactive transport simulations. In column experiments, differences in treatment solution supplied yeast extract concentrations were shown to reliably control the enrichment of indigenous ureolytic microorganisms and achieve a wide range of ureolytic activities. Reactive transport simulations further demonstrated that reductions in stimulated ureolytic rates could enable more uniform improvement and increases in the extent of improvement with reduced sensitivity to changes in solution injection velocities. A reaction-to-injection duration ratio (RTIDR) parameter was proposed and captured the collective impacts of changes in injection rates and ureolytic reaction rates on reactive transport conditions thereby unifying outcomes from both simulations and experiments. A nonuniformity area (NA) parameter was also introduced to quantitatively characterize differences in biocementation uniformity independent of length scale and CaCO3 magnitudes. Results from this study collectively demonstrate the utility of changes in stimulated ureolytic activities towards controlling the spatial uniformity and extent of biocementation over meter-scale distances.

Filling-Balance-Oriented Parameters for Multi-Cavity Molds in Polyvinyl Chloride Injection Molding.

PVC injection molding has constrained temperature and shear rate owing to its temperature sensitivity and high viscosity, as well as its low conductivity. Many challenges are associated with the PVC injection molding process used for producing PVC fittings with a multi-cavity mold. Once filling imbalance occurs, the gates and/or runner of the mold should be changed by machine tools, which is time- and cost-intensive. Using Moldex3D and the Taguchi method, this study reveals an approach to eliminate imbalanced filling of multi-cavity molds for PVC injection molding. The injection rate optimization of the filling stage is successfully verified to reduce the imbalance. Furthermore, the temperatures of the molded PVC fittings are only slightly increased by the change in injection rate. The temperatures of fittings in the filling and packing are lower than the degradation temperature of PVC. This approach may help technicians to obtain pilot-run samples for the optimization of molding parameters and ensure degradation-free PVC molding.

Heavy-Oil Steamflood Validates Machine-Learning-Assisted Model

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 193680, “Implementation and Assessment of Production Optimization in a Steamflood Using Machine-Learning-Assisted Modeling,” by Pallav Sarma, SPE, Ken Lawrence, Yong Zhao, Stylianos Kyriacou, and Delon Saks, Tachyus, prepared for the 2018 SPE International Heavy Oil Conference and Exhibition, Kuwait City, 10–12 December. A physics-based model augmented by machine learning proved its ability to optimize a steam-injection plan in a shallow, heavy-oil field in the San Joaquin Basin of California. The model and a case study to validate its predictive capabilities were described in the previously published paper SPE 185507. Paper SPE 193680 updates the previous case study and presents the results of actual implementation of an optimized steam-injection plan based on the model framework. Introduction The goal of steamflood modeling and optimization is to determine the optimal spatial and temporal distribution of steam injection to maximize future recovery or field economics. Accurate modeling of thermodynamic and fluid-flow mechanisms in the wellbore, reservoir layers, and overburden can be prohibitively resource-intensive for operators, who instead often default to simple decline-curve analysis and operational rules of thumb. The physics-based model described in this paper allows operators to leverage readily available field data to infer reservoir dynamics from first principles. Production, injection, temperature, steam quality, completion, and other engineering data from an active steamflood are continuously assimilated into the model using an ensemble Kalman filter (EnKF). The model is then used to optimize steam-injection rates to maximize or minimize multiple objectives such as net present value (NPV), injection cost, and others, using large-scale evolutionary optimization algorithms. The solutions are low-order and continuous scale, rather than discretized, so modeling, forecasting, and optimization are significantly faster than with traditional simulation. Although steam-floods in the shallow, heavy-oil fields of the San Joaquin Valley have been very successful, the scale of many of these steamfloods also provides optimization opportunities. The basin contains hundreds or even thousands of wells with significant lateral and vertical reservoir heterogeneity, spatial variation of steam quality, varying historical completion quality and methods, and different levels of pattern maturity across the fields. As such, steamflood operations have multiple control variables that can be optimized. Redistribution of steam in existing injectors is one of the most important control variables to optimize in a steam-flood to account for the factors mentioned previously. A successful redistribution optimization produces a list of time-varying injection-rate changes for each injector that can maximize the overall effect of steam on incremental oil production. Additionally, optimizing steam cut across already-mature pat-terns can reduce operational costs. For these crucial decisions, operators typically rely on semiquantitative approaches such as decline-curve analysis or simple analytical models. These methods are capable of using only a small portion of available data and function as rules of thumb, resulting, at best, in qualitatively optimized reservoir management decisions. On the other extreme, some oil companies use sophisticated predictive modeling tools. Reservoir simulation is the most advanced technique available today in that it is capable of integrating disparate data sources and predicting over long-time horizons. While reservoir simulation is an excellent tool for field studies and long-term planning, certain limitations prevent operators from leveraging simulation for day-to-day decision-making.

Shear wave velocity changes induced by earthquakes and rainfall at the Rotokawa and Ngatamariki geothermal fields, Taupō Volcanic Zone, New Zealand

SUMMARY Fluid injection for geothermal production has the potential to produce subsidence and microseismicity that can incur heavy financial cost or hazard. Due to this, novel ways to monitor subsurface deformation to supplement existing methods are highly sought after. We use seismic ambient noise to obtain time-dependent measurements of shear velocity within the geothermal reservoirs of Rotokawa and Ngatamariki, two producing geothermal fields in the Taupō Volcanic Zone located in the central North Island of New Zealand and operated by Mercury Energy. We investigate the relationship between shear wave velocity changes and geothermal injection by selecting time periods at the fields when injection and production volumes were significantly altered: 2009–2010 at Rotokawa, when geothermal injection was quadrupled due to the start-up of a new power station, and 2012–2013 at Ngatamariki, the beginning of geothermal injection for electricity production at that field. Shear wave velocity changes are computed from the ambient noise cross-correlation coda using the Moving Window Cross-Spectral (MWCS) technique, with a reference stack encompassing all data prior to the change in injection rate and moving stacks of 10–50 d. Gradual positive and negative shear velocity changes with a periodicity of approximately 12 months were observed at both sites, with maximum amplitude of 0.06 ± 0.04 and –0.08 ± 0.03 per cent at Rotokawa and 0.07 ± 0.03 and –0.06 ± 0.02 per cent at Ngatamariki. We hypothesize that these changes are due to seasonal rainfall, as seismic velocities computed by ambient noise are sensitive to the filling and emptying of near-surface pore space. In addition to these gradual responses, we found several sharp negative changes in velocity that reach minimum values over a few days and then gradually equilibrate to prior values over a few weeks. The amplitude of these responses is between –0.03 and –0.07 per cent and coincides with regional and local earthquakes. We hypothesize that these responses are primarily produced by the creation of new fractures, the same mechanism that produces gradual groundwater level decreases at regional distances from earthquake epicentres. We analyse a periodic signal within the time-delay measurements and determine that it is at least in part caused by the MWCS window size smoothing the cross-coherence of the ambient seismic signal. We do not observe shear wave velocity changes coinciding with geothermal injection, which may suggest that the signal has lower amplitude compared to the seasonal and seismic responses. We use bandstop filters and polynomial curve fitting to remove the contribution of the seasonal signal, but see no evidence of a shear wave velocity response due to geothermal fluid injection.

Aftershock deficiency of induced earthquake sequences during rapid mitigation efforts in Oklahoma

Induced seismicity provides a rare opportunity to study earthquake triggering and underlying stress perturbations. Triggering can be a direct result of induced stress changes or indirect due to elastic stress transfer from preceding events leading to aftershocks. Both of these processes are observable in areas with larger magnitude induced events, such as Oklahoma. We study aftershock sequences of M2.5 to M5.8 earthquakes and examine the impact of targeted injection rate reductions. In comparing aftershock productivity between California and Oklahoma, we find similar exponential scaling statistics between mainshock magnitude and average number of aftershocks. For events with M≥4.5 Oklahoma exhibits several mainshocks with total number of aftershocks significantly below the average scaling behavior. The sequences with deficient aftershock numbers also experienced rapid, strong mitigation and reduced injection rates, whereas two events with M4.8 and M5.0 with weak mitigation exhibit normal aftershock productivity. The timing of when aftershock activity is reduced correlates with drops in injection rates with a lag time of several days. Large mainshocks with significantly reduced aftershocks may explain decreasing seismicity rates while seismic moment release was still increasing in Oklahoma in 2016. We investigate the expected poroelastic stress perturbations due to injection rate changes within a layered axisymmetric model and find that stresses are lowered by 10s to 100s kPa within the injection-affected zone. For earthquakes induced by poroelastic stress-increase at several kilometers from wells, the rapid shut-in of wells may lead to elastic stress reductions sufficiently high to arrest unfolding aftershock sequences within days after mitigation starts.

Temporal response of magnitude distribution to fluid injection rates in The Geysers geothermal field

The influence of fluid injection rates on the magnitude distribution of the seismicity which occurred in the NW part of The Geysers geothermal site is studied here. A direct comparison between injection rate changes and b value response is attempted after appropriate selection of data subsets. Due to the relatively small sample (1121 events, corresponding to an average rate of ~ 0.45 events/day), we also aggregated seismic activity into two families corresponding to increasing and decreasing injection rates, respectively. The b values were calculated as a function of time lag related to the injection activity. In agreement with previous studies, we found a statistically significant direct relation between b values and injection rate changes, which occurred at a zero or very short time lag (from 0 to ~ 15 days). However, the b value changes are related to the slope (i.e., the second derivative of injection volume), instead of the absolute values of injection rates. The increasing injection rates correspond to b = 1.18 ± 0.06, whereas the decreasing injection rates correspond to b = 1.10 ± 0.05. The corresponding values estimated by the repeated medians technique are b = 1.97 ± 0.20 and b = 1.50 ± 0.13. Both differences are significant at 0.05 level.

Abstract No. 670 Optimal delivery rate and concentration of radiopaque beads for trans-arterial embolization

To determine how changes in the standard injection rate (1.0 mL/min), in the standard concentration (1:9), or the size of the LUMI beads affect the embolization volume. A total of 9 Yorkshire pigs underwent fluoroscopy guided injection of LUMI radiopaque beads using 2 different LUMI bead sizes (R0=40-90 and R1=70-150 microns). Each animal was injected with 1 of 3 bead / Visipaque 320 contrast concentrations (1:4, 1:9, and 1:14) and at 1 of 3 injection rates (0.5mL/min, 1.0mL/min, and 1.5mL/min). Isovue contrast was used to position the catheter and allow for direct injection of the embolization beads into the arterial branch of the liver and kidneys. The larger LUMI beads (70-150 microns) were used to embolize the left kidneys and left hepatic lobes and the smaller LUMI beads (40-90 microns) were used to embolize the right kidneys and right hepatic lobes. The animals were subsequently euthanized. The distance of the beads from the hilum was then evaluated with imaging and pathological correlation. Technical success rate was 100% (36/36). Embolization was achieved regardless of the injection rate and concentration. The complication rate after the embolization process was 0% (0/36). When measuring the effect of concentration on embolization volume, higher concentrations correlated with decreased embolization volumes in both the liver and kidney (P = .018 and P = .001, respectively). Smaller bead sizes also correlated with decreased embolization volume in both the liver and kidney (P = .014 and P = .048, respectively). However, different injection rates did not result in a statistically significant difference in embolization volume in either the liver or kidney (P = .393 and P = .338, respectively). Increased concentration and smaller bead sizes appear to decrease embolization volume. However, changes in the injection rate do not appear to affect the embolization volume.

Temporal static stress drop variations due to injection activity at The Geysers geothermal field, California

AbstractWe use a high‐quality data set from the NW part of The Geysers geothermal field to determine statistical significance of temporal static stress drop variations and their relation to injection rate changes. We use a group of 322 seismic events which occurred in the proximity of Prati‐9 and Prati‐29 injection wells to examine the influence of parameters such as moment magnitude, focal mechanism, hypocentral depth, and normalized hypocentral distances from open‐hole sections of injection wells on static stress drop changes. Our results indicate that (1) static stress drop variations in time are statistically significant, (2) statistically significant static stress drop changes are inversely related to injection rate fluctuations. Therefore, it is highly expected that static stress drop of seismic events is influenced by pore pressure in underground fluid injection conditions and depends on the effective normal stress and strength of the medium.

Rupture Process of theMw 5.8 Pawnee, Oklahoma, Earthquake from Sentinel‐1 InSAR and Seismological Data

ABSTRACT Since 2009, Oklahoma has experienced a soar in induced seismicity, a side effect of extensive saltwater injection into subsurface sedimentary rocks. The seismic hazard entailed by these regional‐scale injection operations is, however, difficult to assess. The 3 September 2016 M w 5.8 Pawnee earthquake is the largest since the increase of seismic activity. The event was preceded by an m b 3.2 foreshock two days prior, and changes in injection rates have been reported on wastewater disposal wells located less than 10 km from the epicenter, suggesting that the earthquake may have been induced. Using Sentinel‐1 spaceborne interferometric synthetic aperture radar, we unambiguously show that the earthquake produced peak‐to‐peak line‐of‐sight displacement of 3 cm at the surface. Kinematic inversion of geodetic and seismological data shows that the main seismic rupture occurred between a depth of 4 and 9 km, over a length of 8 km, with slip reaching at least 40 cm. The causative fault is entirely buried within the Precambrian basement, that is, well beneath the Paleozoic sedimentary pile where injection is taking place. Potentially seismogenic faults in the basement of Oklahoma being poorly known, the risk of M w ≥6 events triggered by fluid injection remains an open question.

INJECTION PROPAGATION MODEL IN SANDY SOIL

This articles focuses on the process of injection solution in the sand as physical phenomena. During theoretical studies of the propagation of the fluid phase in a porous medium, actual is the definition of the parameters of the jet, necessary for layer material discontinuity in the contact zone of the jet to the surface. It can be achieved through the injection process modeling in a dispersion medium by constructing geometrical similarity of injection jet. It is found that the propagation of the fluid phase in the solid body pores suggests that as they reach the point at the distance from the injector to the «end» of the jet in pores pre-saturated by water, gradual change in injection rate depending on the initial rate of efflux and viscosity occurs.

Fieldwide Determination of Directional Permeabilities Through Transient Well Testing

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 181437, “Fieldwide Determination of Directional Permeabilities Using Transient Well Testing,” by Yan Pan, Medhat Kamal, and Wayne Narr, Chevron, prepared for the 2016 SPE Annual Technical Conference and Exhibition, Dubai, 26–28 September. The paper has not been peer reviewed. Knowledge of the maximum- and minimum-permeability directions in anisotropic reservoirs helps to optimize injector and producer locations and is important for reservoir management, especially under secondary or enhanced recovery of hydrocarbons. The complete paper describes a method using transient-test data rich with dynamic information aiming to provide fieldwide permeability distribution in well-spacing scale, which is relevant for estimating fluid movement and recovery. Introduction The knowledge of flow communication between wells is key information for reservoir management, especially in secondary or tertiary recovery. The surveillance methods to collect dynamic data to gain such knowledge include multiple-well pressure-transient tests and tracer tests. The measurements of tracer agents arriving at producing wells provide direct confirmation of flow communication. Interwell transient tests derive similar information through the measurement of pressure responses (at observation wells) to the production- or injection-rate changes at an active well, and the time required to conduct such tests is much shorter than the time required to conduct tracer tests. For anisotropic reservoirs, such as naturally fractured fields or channel systems, knowing the permeability tensor directions and the ratios of the maximum to the mini-mum permeability in various locations in the field provides better opportunities to make optimal operational decisions. All previously proposed methods in the literature require three sets of interference or pulse tests among wells offset at different azimuths, and the pressure-response data are analyzed simultaneously using type-curve matching to calculate permeability tensors. In practice, there is limited opportunity to conduct all three sets of interference tests through the same well at one time and to analyze them simultaneously to derive a permeability tensor. In the complete paper, a new method is proposed that uses previous test-analysis results directly to estimate the permeability tensor. The analysis results (the permeability and porosity of the fast path linking two wells) from a single set interwell (interference or pulse) test could be obtained using any modern techniques with analytical, semi analytical, or numerical models and would not be limited to conventional type-curve matching. The algorithm uses mathematical matrix operations, and all analysis results can be integrated to generate the field permeability-tensor map. Mathematical aspects of the method, as well as method validation, are discussed in the complete paper.

포천 화강암의 결 이방성이 수압파쇄거동에 미치는 영향

본 연구에서는 화강암 내부의 미세균열 분포에 따른 이방성이 수압파쇄실험 결과에 미치는 영향을 평가하였다. 압력증가율을 일정하게 설정하여 수압파쇄실험을 수행한 결과, 원주방향(주입정 방향과 직교)으로 리프트면이 분포한 시료의 파쇄압력이 가장 낮게 측정되었고, 이는 미세균열의 밀도가 높기 때문이다. 수압파쇄실험과정에서 시료 내부의 변화가 발생하는 주입압력의 크기와 유체 주입속도의 변화 또한 결방향에 따라 분포한 미세균열의 밀도와 관계가 있는 것으로 판단된다. 유체주입속도를 일정하게 설정하여 수압파쇄실험을 수행하였을 경우, 상대적으로 미세균열의 밀도가 높은 리프트면이 원주방향으로 분포된 시료에서 주입압력증가율이 낮게 나타났고, 유체가 침투될 수 있는 균열망이 상대적으로 적게 형성된 그레인면 및 하드웨이면이 원주방향으로 분포된 시료에서는 압력증가율이 높게 나타났다. X-ray CT 촬영을 통해 시료 내부에 생성된 균열의 방향을 확인한 결과, 대부분의 시료에서 리프트면 혹은 그레인면과 평행한 방향으로 균열이 생성된 것을 확인하였고, 이는 암석 내에 상대적으로 미세균열의 밀도가 높아서 분리성이 크기 때문이다. In this study, laboratory hydraulic fracturing tests are carried out to evaluate the effects of the cleavage anisotropy of Pocheon granite. Breakdown pressure is smaller when cracks are generated to the direction of rift plane in constant pressurization rate condition because of higher microcracks density. Besides not only injection rate changes but also the amount of injection pressure for fracture initiation and crack expansion is detected while testing due to internal deformation. Pressurization rate is higher while hydraulic fracture testing with constant injection rate condition in case of the specimen which has rift plane perpendicular to borehole because there are much flow paths to penetrate compared to the specimen which has hardway plane perpendicular to borehole. Observation by X-ray CT scanning shows that almost all of cracks due to hydraulic fracturing are generated to the direction of plane which has higher microcrack density that is rift plane or grain plane.

Velocity‐saturation relation in partially saturated rocks: Modelling the effect of injection rate changes

ABSTRACTThe relationship between P‐wave velocity and fluid saturation in a porous medium is of importance for reservoir rock characterization. Forced imbibition experiments in the laboratory reveal rather complicated velocity–saturation relations, including rollover‐like patterns induced by injection rate changes. Poroelasticity theory‐based patchy saturation models using a constant fluid patch size are not able to describe these velocity–saturation relations. Therefore, we incorporate a saturation‐dependent patch size function into two models for patchy saturation. This recipe allows us to model observed velocity–saturation relations obtained for different and variable injection rates. The results reveal an increase in patch size with fluid saturation and show a reduction in the patch size for decreasing injection rate. This indicates that there can exist a distinct relation between patch size and injection rate. We assess the relative importance of capillarity on velocity–saturation relations and find that capillarity stiffening impairs the impact of patch size changes. Capillarity stiffening appears to be a plausible explanation when a decrease in the injection rate is expected to boost the importance of capillarity.

An objective method for the assessment of fluid injection‐induced seismicity and application to tectonically active regions in central California

AbstractChanges in seismicity rates, whether of tectonic or of induced origin, can readily be identified in regions where background rates are low but are difficult to detect in seismically active regions. We present a novel method to identify likely induced seismicity in tectonically active regions based on short‐range spatiotemporal correlations between changes in fluid injection and seismicity rates. The method searches through the entire parameter space of injection rate thresholds and determines the statistical significance of correlated changes in injection and seismicity rates. Applying our method to Kern County, central California, we find that most earthquakes within the region are tectonic; however, fluid injection contributes to seismicity in four different cases. Three of these are connected to earthquake sequences with events above M4. Each of these sequences followed an abrupt increase in monthly injection rates of at least 15,000 m3. The probability that the seismicity sequences and the abrupt changes in injection rates in Kern County coincide by chance is only 4%. The identified earthquake sequences display low Gutenberg‐Richter b values of ∼0.6–0.7 and at times systematic migration patterns characteristic for a diffusive process. Our results show that injection‐induced pressure perturbations can influence seismic activity at distances of 10 km or more. Triggering of earthquakes at these large distances may be facilitated by complex local geology and faults in tectonically active regions. Our study provides the first comprehensive, statistically robust assessment of likely injection‐induced seismicity within a large, tectonically active region.

Regional detection and monitoring of injection-induced seismicity: Application to the 2010–2012 Youngstown, Ohio, seismic sequence

Increased rates of seismicity in tectonically quiescent regions like the midcontinent region of the United States have been hypothesized to be related to human activities such as oil and gas production and wastewater injection. It can be difficult to establish how human activities relate to earthquakes, particularly when local seismic networks are not available to provide a high-quality characterization of the seismic sequence in question. Here, we use a multistation waveform crosscorrelation approach to evaluate the relationships between earthquakes associated with the 2011–2012 Youngstown, Ohio, seismic sequence and the injection history of a local wastewater disposal well. By using data recorded by four regional seismic stations 50–200 km (31–124 mi) away from Youngstown, we demonstrate that high-resolution results can be achieved without using costly and scientifically focused local seismic deployments. Compared to the number of events recorded using standard detection methodologies, we realize a 25-fold increase in detected seismicity (282 detected events) during the sequence, and allow us with confidence to interpret a direct link between seismicity and well injection volumes. Using a combination of absolute and relative location techniques, we demonstrate that seismicity migrated from below the injection well toward the west, along a line consistent with a nodal plane of the largest earthquake in the sequence. We are able to separate the seismic sequence into three distinct phases, consistent with changes in injection rates and maximum injection pressures. In addition, using daily injection volume records, we can identify two families of similar earthquakes. The first family occurred early in the sequence and close to the injection well and was followed by a recurrence pattern that lagged injection activity by 1 day. The second family. which occurred later in the sequence and farther from the well, displayed a 4-day lag. We interpret these relationships to be related to pore-pressure diffusion rates within the fault network responsible for the seismicity. Collectively, our technique shows the high quality of results possible when only a few regional seismic stations are available for monitoring.

Experimental study on the injection characteristics of dimethyl ether–biodiesel blends in a common-rail injection system

The injection rate and dynamic behaviour during and after the injection of dimethyl ether–biodiesel blends in a common-rail injection system are experimentally studied. The characteristics of the instantaneous line pressure evolution induced by the injection are obtained. In comparison with the injection of biodiesel, the injection of 100 wt % dimethyl ether starts later, but the starts of injection of other fuels are almost at the same time. Increasing the dimethyl ether blending ratio leads to a retarded end of injection and a significantly prolonged injection duration, but the peak injection rate changes little. With increasing rail pressure, the early rate of change in the injection rate with time and the peak injection rate increase, and the injection rate fluctuates more strongly. With increasing energizing time, the start of injection and the peak injection rate remain unchanged. The curves of the line pressure fluctuations at the injector inlet are similar for all dimethyl ether–biodiesel blends. When the dimethyl ether blending ratio is increased from 30 wt % to 100 wt %, the drop in the amplitude of the line pressure at the start of injection becomes smaller, the peak pressure decreases gradually and the phase is retarded. The duration of the line pressure fluctuations after injection becomes longer with increasing dimethyl ether blending ratio. By increasing the rail pressure, the line pressure at the start of injection drops more quickly, with a larger amplitude. At the end of injection, the magnitude of the peak pressure increases with an advanced phase, and the duration of the pressure fluctuations increases. By increasing the energizing time, the line pressure drop at the start of injection is unchanged, and the first line pressure peak increases with a retarded phase.

Measurement of advective soil gas flux: results of field and laboratory experiments with CO2

A multi-channel, steady-state flow-through (SSFT), soil-CO2 flux monitoring system was modified to include a larger-diameter vent tube and an array of inexpensive pyroelectric non-dispersive infrared detectors for full-range (0–100 %) coverage of CO2 concentrations without dilution. Field testing of this system was then conducted from late July to mid-September 2010 at the Zero Emissions Research and Technology project site located in Bozeman, Montana, USA. Subsequently, laboratory testing was conducted at the Pacific Northwest National Laboratory in Richland, WA, USA using a flux bucket filled with dry sand. In the field, an array of 25 SSFT and 3 non-steady-state (NSS) flux chambers was installed in a 10 × 4 m area, the long boundary of which was directly above a shallow (2-m depth) horizontal injection well located 0.5 m below the water table. Two additional chambers (one SSFT and one NSS) were installed 10 m from the well for background measurements. Volumetric soil moisture sensors were installed at each SSFT chamber to measure mean moisture levels in the top 0.15 m of soil. A total flux of 52 kg CO2 day−1 was injected into the well for 27 days and the efflux from the soil was monitored by the chambers before, during, and for 27 days after the injection. Overall, the results were consistent with those from previous years, showing a radial efflux pattern centered on a known “hot spot”, rapid responses to changes in injection rate and wind power, evidence for movement of the CO2 plume during the injection, and nominal flux levels from the SSFT chambers that were up to sevenfold higher than those measured by adjacent NSS chambers. Soil moisture levels varied during the experiment from moderate to near saturation with the highest levels occurring consistently at the hot spot. The effects of wind on measured flux were complex and decreased as soil moisture content increased. In the laboratory, flux-bucket testing with the SSFT chamber showed large measured-flux enhancement due to the Venturi effect on the chamber vent, but an overall decrease in measured flux when wind also reached the sand surface. Flux-bucket tests at a high flux (comparable to that at the hot spot) also showed that the measured flux levels increase linearly with the chamber-flushing rate until the actual level is reached. At the SSFT chamber-flushing rate used in the field experiment, the measured flux in the laboratory was only about a third of the actual flux. The ratio of measured to actual flux increased logarithmically as flux decreased, and reached parity at low levels typical of diffusive-flux systems. Taken together, the results suggest that values for advective CO2 flux measured by SSFT and NSS chamber systems are likely to be significantly lower than the actual values due to back pressure developed in the chamber that diverts flux from entering the chamber. Chamber designs that counteract the back pressure and also avoid large Venturi effects associated with vent tubes, such as the SSFT with a narrow vent tube operated at a high chamber-flushing rate, are likely to yield flux measurements closer to the true values.

Manage Fields With Intelligent Surveillance, Production Optimization, and Collaboration

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 150079, ’Managing Fields Using Intelligent Surveillance, Production Optimization, and Collaboration,’ by Frans G. Van den Berg, SPE, Andrew Mabian, SPE, Ronald Knoppe, Edwin Van Donkelaar, Frans Terlaan, and Valentin Koldunov, SPE, Shell, and Rufina Lameda, Science Applications International Corporation, prepared for the 2012 SPE Intelligent Energy International, Utrecht, The Netherlands, 27-29 March. The paper has not been peer reviewed. Asset professionals in Shell use advanced technologies and processes for field management and optimizing production performance. Real-time monitoring of wells and compressors has become the norm, delivering higher uptime and increased production. Wells and facilities with events or deviations (i.e., exceptions) are highlighted, enabling staff to focus on fixing critical wells and facilities. The information is brought together in collaborative work environments (CWEs) with a video connection to streamline communication between field and office, and to expedite decision making. Introduction In general, all of Shell’s new field developments, and redevelopments of existing fields, are equipped with appropriate smart-fields solutions. The elements selected in each field depend on its features and conditions. A screening process is carried out in the early stages of the project to identify requirements and opportunities for implementation. In some cases, application has changed the development concept completely (e.g., field development with smart wells and a remotely controlled platform). In other cases, solutions help improve field management. Salym Development Applications were implemented in the West Salym field in western Siberia, Russia. West Salym is the largest of three fields in the Salym Petroleum Development (Fig. 1). Since 2003, approximately 600 wells have been drilled, of which approximately 450 are producers and 150 are water injectors. Field production peaked in 2011 at approximately 180,000 B/D. Production decline would start within 5 years, and production was expected to continue for another 10–15 years. The wells were drilled from drilling pads, each with 16–20 well slots. Each production well was equipped with an electrical submersible pump (ESP) and a variable drive control. The frequency of the ESPs (and, hence, the pump rate) was optimized weekly for production optimization and ESP-performance optimization and to keep the drawdown on the wells constant and the reservoir pressure above the bubblepoint. Frequent adjustments of the ESP settings were required because the reservoir responded fast to any changes in injection rates.