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Clayey-silty hydrate-bearing sediments are widely distributed worldwide, presenting significant potential for natural gas hydrate (NGH) extraction. However, fundamental thermodynamic and kinetic properties of CH 4 hydrate (MH) within these sediments remain subjects of debate, necessitating further investigation. This study aimed to investigate the kinetics of MH formation and dissociation in clayey-silty sediments suspensions, alongside morphological examinations. Results demonstrated that SH-W02-B sediments (SS) effectively shorted the induction time (t ind), with even a minute mass fraction of 0.1 wt% SS reducing t ind by 14 min compared to pure water (41 min). Lower mass fractions (<5.0 wt%) exhibited slight promotion of MH growth kinetics, whereas higher mass fractions (>10.0 wt%) markedly promoted MH growth kinetics, peaking at 144 v/v (20.0 wt%), correspondingly, and facilitating the conversion of H 2 O to MH to ∼70%. Morphological observation unveiled the formation of a thin clay layer at the gas-liquid interface, retarding MH formation and inducing the development of an anti-seepage hydrate layer, leading to the initial slow growth phase. Subsequent upward water migration facilitated the transport of fine clay particles, while the progressive encasement of clay particles by hydrate disrupted the fine clay layer, triggering the rapid hydrate formation phase and ensuing stratification between fine and coarse sediments particles. During hydrate dissociation, a heterogeneous distribution of fine and coarse sediments particles manifested in the reservoir. Moreover, the results carrying profound implications on understanding NGH occurrence pattern and developing recovery strategies from clayey-silty hydrate-bearing sediments. [Display omitted] • Clayey-silty core sediments were recovered near the China second field production test well. • X-ray diffraction analysis reveals 31 wt% clay with primary illite/smectite mixed layer in core sediments. • The presence of core sediments expedite CH 4 hydrate nucleation and enhance the growth kinetics. • Transport of fine clay particles leads to two-stage growth with stratified hydrate-sediments layers. [ABSTRACT FROM AUTHOR]

• Four cooling regimes were employed to form CH 4 -hydrate bearing sediments. • All four multi-stage cooling regimes result in heterogeneous distribution of S H. • Heat inflow on the spatial distribution of S H (hydrate saturation) is significant. • Perfect insulation improves the uniformity of all phases in hydrate-bearing cores. Laboratory-created samples of methane hydrate (MH)-bearing media are a necessity because of the rarity and difficulty of obtaining naturally-occurring samples. The hypothesis that the inevitable heterogeneity in the phase saturations of the laboratory samples may lead to unreliable and non-repeatable results provided the impetus for this study, which aimed to determine the conditions under which maximum uniformity can be achieved. To that end, we designed four experiments involving different multi-stage cooling regimes (in terms of their duration and number of stages) to induce MH formation under excess-water conditions. In the absence of direct visualization capabilities, we analysed the experimental results by means of numerical simulation, which provided high-resolution predictions of the spatial distributions of the phase saturations in the cores and enabled the estimation of the parameters controlling the kinetic MH-formation behaviour through history-matching. Analysis of the numerical results indicated that, under the conditions of the experiments and with the design of the reactor, significant heterogeneities in phase saturation distributions were observed in all cases, leading to the conclusion that it is not possible to obtain cores with uniform phase saturation. Additionally, contrary to expectations, heterogeneities increased with the number of cooling stages and the duration of cooling, and this was attributed to imperfect insulation of the upper part of the reactor. A set of simulations involving perfect insulation of the reactor top confirmed the validity of this assumption: (a) predicting the formation of high-uniformity MH-bearing cores that became more homogeneous as the number of cooling stages and the length of the cooling period increased; and (b) providing important information for the improvement of the standard design of the experimental apparatus for the laboratory creation of MH-bearing cores using the excess water method. [ABSTRACT FROM AUTHOR]

Highlights • Numerical analysis of MH dissociation and fluids production by depressurization. • A function describing the change in MH surface area is incorporated in the T+H code. • Flow, thermal, kinetic parameters are optimized using a history-matching technique. • Simulation validated by experiment elucidates the issue of spatial heterogeneity. Abstract Methane Hydrates (MHs) are a promising energy source abundantly available in nature. Understanding the complex processes of MH formation and dissociation is critical for the development of safe and efficient technologies for energy recovery. Many laboratory and numerical studies have investigated these processes using synthesized MH-bearing sediments. A near-universal issue encountered in these studies is the spatial heterogeneous hydrate distribution in the testing apparatus. In the absence of direct observations (e.g. using X-ray computed tomography) coupled with real time production data, the common assumption made in almost all numerical studies is a homogeneous distribution of the various phases. In an earlier study (Yin et al., 2018) that involved the numerical description of a set of experiments on MH-formation in sandy medium using the excess water method, we showed that spatially heterogeneous phase distribution is inevitable and significant. In the present study, we use as a starting point the results and observations at the end of the MH formation and seek to numerically reproduce the laboratory experiments of depressurization-induced dissociation of the spatially-heterogeneous MH distribution. This numerical study faithfully reproduces the geometry of the laboratory apparatus, the initial and boundary conditions of the system, and the parameters of the dissociation stimulus, capturing accurately all stages of the experimental process. Using inverse modelling (history-matching) that minimized deviations between the experimental observations and numerical predictions, we determined the values of all the important flow, thermal, and kinetic parameters that control the system behaviour, which yielded simulation results that were in excellent agreement with the measurements of key monitored variables, i.e. pressure, temperature, cumulative production of gas and water over time. We determined that at the onset of depressurization (when the pressure drop – the driving force of dissociation – is at its maximum), the rate of MH dissociation approaches that of an equilibrium reaction and is limited by the heat transfer from the system surroundings. As the effect of depressurization declines over time, the dissociation reaction becomes kinetically limited despite significant heat inflows from the boundaries, which lead to localized temperature increases in the reactor. [ABSTRACT FROM AUTHOR]

We analyse numerically an earlier experimental study that involved the formation of methane hydrates by the excess water method in a small reactor filled with a sandy porous medium, and seek to address questions about the type of the hydration reaction and the phase heterogeneity in the resulting hydrate-bearing sand. Using a fine discretization describing the reactor assembly, the experimental process is faithfully replicated numerically. The multi-stage process of hydrate formation is subdivided in 7 steps. The experimental data from the continuously-monitored pressure and temperature during each step are used for comparison against the numerical predictions, the identification of the dominant processes and the determination of the associated parameters through a history-matching process that minimizes deviations between observations and simulation results. The results of this first-ever study on this subject demonstrate unequivocally that the hydration reaction is a kinetic (as opposed to an equilibrium) process, and that the spatial distributions of the various phases (aqueous, gas and hydrate) at the end of the formation process are strongly heterogeneous. This has serious implications in simulation studies of hydrate dissociation that assume uniform initial phase saturation distributions. The history-matching process indicates that (a) the system behaviour is sensitive to some flow parameters (porosity and irreducible water saturation) only during the first water injection, (b) it is insensitive to the sand intrinsic permeability during all steps of the study, and (c) thermal processes dominate after the first water injection, yielding estimates of the thermal properties of the sand and of time-variable key parameters of the kinetic reaction. [ABSTRACT FROM AUTHOR]

A huge amount of natural gas hydrates remains untapped in permafrost and continental margin. While several short term field production tests have been carried out, the underlying challenges during hydrate dissociation in porous media, such as the interdependent production behavior of gas and water, is still not well understood. In this work, we employed depressurization technique to recover natural gas from a water saturated hydrate bearing sediment (40% S H , 50% S A and 10% S G ) at 281.5 K surrounding temperature. During depressurization, the bottom hole pressure (BHP) was maintained at constant pressures of 5.0, 4.0, 3.0 and 2.1 MPa respectively to evaluate its effect on gas and water production. As expected, a higher BHP (corresponding to a lower dissociation driving force) resulted in a slower gas and water production. At a BHP of 2.1 MPa, thermal buffering was observed below ice point (272.7 K), accompanied by enhanced gas production. By lowering BHP from 5.0 MPa to 2.1 MPa, the percentage methane produced increased from 45.5% to 83.0%; whereas the cumulative water production decreased from 217 mL to 157 mL. The difference in gas and water production was attributed to the preferential production of aqueous phase at higher BHPs (5.0 and 4.0 MPa) nearing the end of hydrate dissociation whereby less hydrates were present. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrate-bearing sediments under excess-water condition were synthesized systematically. • Fluid production induced by depressurization below the quadruple point were examined. • Effect of pressure drawdown rate and hydrate phase saturation were investigated. • Both gas production rate and recovery ratio increased under ultra-deep depressurization. Driven by the large resource volume, extraction of CH 4 from hydrate reservoirs has received worldwide attention. Depressurization is a feasible method and has been widely used in past field tests. However, fluid production behavior from water-saturated hydrate-bearing sediments below the quadruple point of CH 4 + H 2 O has not been well understood and warrants investigation. In this study, we designed a series of experiments using ultra-deep depressurization with bottom hole pressure (BHP) of 1.0 MPa, 1.5 MPa and 2.1 MPa in water-saturated hydrate-bearing sediments to investigate the fluid production behavior, particularly in the region with potential ice or secondary hydrate formation. The effect of hydrate saturations and pressure drawdown rates on fluid production below the quadruple point were systematically examined. Our experimental results show that ice formation was likely based on the temperature response, however, the self-preservation effect by ice formation prevents a further drop in temperature to its equilibrium temperature at the corresponding BHP. The gas and water recovery ratios increased by 6.5% and 49.1%, respectively for BHP below the quadruple point. No significant benefit of water trapping due to ice formation was observed. Faster pressure drawdown rate results in a more substantial temperature drop, which could trigger ice formation. Still, interestingly gas production was continuous and not affected in the phase diagram of ice + CH 4. Higher hydrate phase saturation improves gas production rate and final gas recovery ratio, yielding a lower water-gas ratio for more economic-viable CH 4 recovery. Our results indicate that ultra-deep depressurization could be one technical feasible option for increasing both gas production rate and final recovery ratio. The findings provide valuable information for designing an ultra-deep depressurization scheme based on S H of interest in future production tests. [ABSTRACT FROM AUTHOR]

• Integrated history-matching workflow coupling PSO with T + H v1.5 was developed. • Composite thermal conductivity of hydrate-bearing sands was estimated. • Bejan model shows superiority than Somerton model in depicting temperature response. • Optimal composite thermal conductivity yielded is 2.16 W/mK with S H = 0.40. • Particle size over 20 and maximum velocity coefficient 0.5 in PSO is recommended. Knowledge of the thermophysical properties of methane hydrate-bearing sediments (MHBS) plays a critical role in the evaluation of fluid production potential from gas hydrate accumulations in geologic media. The process of estimating the values of key flow and transport parameters related to MHBS is of great importance. In this paper, we developed an integrated optimization workflow by integrating a global optimization algorithm, specifically particle swarm optimization (PSO) with the TOUGH+Hydrate v1.5 hydrate simulator. The optimization technique was employed to estimate the composite thermal conductivity of MHBS (λ MHBS) through history-matching the simulated results with the experimental observation over time automatically in a process of stepwise heating an aqueous-rich heterogeneous MH-bearing core sample (S H = 0.40 and S A = 0.57) at P = 7.0 MPa. Two different composite models were tested and compared for their performance in predicting the temperature response. A sensitivity study was conducted to provide guidance on the selection of PSO parameters to accelerate the convergence speed. The optimal λ MHBS obtained from the Bejan linear model is 2.16 W/mK with an absolute average deviation (AAD) of 2.66%, which is superior than the Somerton nonlinear model. Based on the results from the sensitivity study, the coupling of PSO algorithm with T+H v1.5 was proved to be robust and reliable. It is found that a particle size over 20, a maximum velocity coefficient around 0.5 and a well-defined parameter range guided by literature improves the efficiency in searching the optimal solution, achieving a global best cost with fewer iterations. The optimization procedure developed in this paper can be adopted in estimation of other groups of parameters related to MH-bearing systems (i.e. thermal, flow, geomechanical properties and the kinetic rate parameters of MH reactions) and in the optimization of production strategies from MH reservoirs (e.g. well positioning, pressure drawdown level and rate, etc.) to improve the energy efficiency of the production process. [ABSTRACT FROM AUTHOR]

• Hydrate-bearing sediments with saturation above 0.40 was synthesized consistently. • Three drawdown rates were employed to induce hydrate dissociation and fluid production. • Two-stage water production and continuous gas production profiles were observed. • Cumulative water production rate increases linearly with drawdown rate. • Gas recovery of 0.83 and water recovery of 0.26 were attained at BHP = 3.0 MPa. Methane hydrates have been considered as the future source of energy due to its vast resource volume and high energy density. Depressurization has been demonstrated to be a technical feasible method in producing gas from hydrate reservoirs in the past field production tests. However, major technical challenges, i.e. low gas production rate, excessive water production, and uncontrollable sand production remain. Such undesirable production behaviour is directly linked to one key process variable, the rate of pressure drawdown. It controls the rate of hydrate dissociation and governs the multiphase fluid flow in sandy media. However, precise control of bottom hole pressure in large-scale production tests is difficult and it remains unclear how different drawdown rates affect the fluid production behaviour. Herein, we performed a series of hydrate formation experiments synthesizing aqueous-rich methane hydrate-bearing sediments with hydrate saturation above 40% and subsequently a series of depressurization experiments employing different controlled drawdown rates to dissociate the hydrate-bearing samples. Cumulative production of gas and water were monitored during the depressurization. The goals of the experiments were to examine the fluid production rate, the recovery ratio, and the temperature response in the hydrate-bearing system under different drawdown strategies. Cumulative water production rate increases linearly with drawdown rate, while cumulative gas production rate is directly linked to the hydrate dissociation rate, which is controlled by heat transfer at the early stage and dissociation kinetics toward the final stage. Water gas ratio can be regulated within a threshold by employing a slow drawdown rate. In addition, the final recovery of fluid is not controlled by the drawdown rates but is related to the final stable conditions of pressure and temperature. Our findings expand the understanding of fluid production behaviour from hydrate-bearing sediments and provide guidance in optimizing production strategies and in assessing the fluid production potential for future experiments and field production tests from hydrate reservoirs. [ABSTRACT FROM AUTHOR]

• Fluid production from uniform and non-uniform hydrate-bearing samples is compared. • Assumption of uniformity results in slower rate of cumulative production of water. • Sensitivity analysis on controlling mechanisms of fluid production is conducted. • Gas production is dominated by thermal conductivity and kinetic rate parameters. • Water production is sensitive to absolute permeability and kinetic rate parameters. Methane hydrates (MHs) have been considered as the future source of energy because of its vast resource volume and high energy density. Energy recovery from MH-bearing sediments has attracted intensifying research activities. Fundamentally, heat transfer, fluid flow through porous media, and the kinetics of hydrate reaction are the three key processes controlling the behavior of MH dissociation and the associated fluid production. Earlier studies have suggested that heterogeneous spatial distribution of S H is inevitable in MH-bearing samples synthesized in laboratory. In this paper, we extend our study to analyze numerically the simulation results from the two realizations of the samples (homogeneous and heterogeneous) to identify differences in the fluid production and to determine if they are sufficiently different. Additionally, we conduct a sensitivity analysis and a statistical analysis on the key transport and kinetic rate parameters that could affect hydrate dissociation and fluid production in the context of a heterogeneous hydrate-bearing sample, in an effort to provide insights that could lead to improved designs for laboratory experiments and (possibly) field applications. Our results suggest that the approximation of an artificial hydrate-bearing core with heterogeneous phase saturations by an assumption of uniform phase saturation distributions results in practically similar fluid production profile except for the very early stage with maximum 20.0% deviation in the water production. From the sensitivity and statistical analysis, we determine that gas production depends strongly on the kinetic rate constant, K d 0 and the composite thermal conductivity of the hydrate-bearing sediments, λ θ ; while, water production is very sensitive to K d 0 and the absolute permeability of the sandy medium, k. Understanding the effect of phase heterogeneity and the relative importance of key parameters on the production behavior of hydrate-bearing sediments could provide basis for novel production technologies that lead to enhanced gas production and energy efficiency in the energy recovery process. [ABSTRACT FROM AUTHOR]

• Five different wellbore designs are employed in production from hydrate-bearing sediments. • Continuous gas production and step-wise water production are observed at all pressures. • Slotted-liner design offers better control of water production than bore-hole design. • Partial perforation and perforation location affect water production more than gas production. Methane hydrates have been considered as the future clean energy resource. To recover energy from hydrate-bearing sediments safely and effectively requires a fundamental understanding of the dynamic behaviour of hydrates in sandy media. Past field production tests have proved the technical feasibility of gas production from hydrate reservoirs. However, technical challenges (e.g. sand production and excessive water production) remain in realizing long-term economic-viable production. In this study, we investigate the effect of various wellbore designs (specifically the shape and the location of perforations) on the fluid production behaviour in aqueous-rich hydrate-bearing sediments. Slotted-liner design was first-time incorporated in depressurization under different bottom-hole pressures (2.5 MPa, 3.0 MPa and 4.0 MPa). Continuous gas production and step-wise water production during the early stage of depressurization were observed at all pressures because of the change of fluid flow path from reservoir to wellbore. Compared with traditional borehole design, slotted-liner design showed advantage in controlling water production under low BHP (2.5 MPa). Using wellbores with different perforation locations, it was observed that perforation location does not pose a significant impact on the behaviour of gas production; whereas, middle perforation away from the aqueous-rich and hydrate-rich region yielded the least water production. The experimental results from this study demonstrated the possibility of employing slotted-liner well and varying the perforation location in reducing water production from methane hydrate-bearing sediments. Our findings can pave way for the testing of novel wellbore designs to further enhance gas recovery and reduce water production from hydrate reservoirs. [ABSTRACT FROM AUTHOR]

Highlights • Vertical wellbore was incorporated within water saturated hydrate sediment. • Hydrate accumulation around wellbore reduced gas production and dissociation rate. • Cumulative gas production enhanced by up to 8% through vertical wellbore. • Simultaneously, water production was reduced by up to 43% at 4.5 MPa. Abstract Natural gas hydrates, an abundant source of natural gas in nature, have the potential of supplying energy for the future. However, due to the complexity of physical processes that occur simultaneously during the dissociation of hydrates within porous media, further understanding on the dynamic behavior of hydrates dissociation (e.g. heat transfer associated with phase transition, permeability changes, and simultaneous gas/water production) is required to elucidate the process of gas recovery from hydrates. In this work, we investigate the effect of a single vertical wellbore incorporation on the production behavior from hydrates formed in sandy sediments (0.1–0.5 mm). Depressurization approach (3.5, 4.0 and 4.5 MPa) was applied to dissociate the hydrate-bearing sand at a constant surrounding temperature of 281.5 K. Through the incorporation of a vertical wellbore, the gas production rate decreased with increasing bottom hole pressure, and continuous production of gas was observed at 4.5 MPa even after 10 h of dissociation. For water production, a majority of water was produced within the first 2 h, beyond which only a small amount of water was recovered. It was also observed that the incorporation of a vertical wellbore in the current design and apparatus impeded hydrate dissociation, which was attributed to a stronger flow resistance for fluids to exit through the vertical wellbore. Cumulatively, the incorporation of vertical wellbore enhanced gas production by up to 8% and reduced water production by up to 42%. In the future, innovative production schemes, such as heated wellbore and hydraulic fracturing can be applied to further optimize gas production from hydrate-bearing sediments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrical resistivity can quantify the real-time TBAB hydrate fraction in slurry. • Sequential phase transition from type A to type B TBAB hydrate was observed. • From 278.2 K to 274.2 K, the hydrate growth rate was enhanced by 2.5 times. • L-tryptophan enhanced TBAB hydrate formation at 500 ppm but inhibited at 1000 ppm. Tetra-n-butylammonium bromide (TBAB) semi-clathrate hydrate has a large latent heat and suitable phase transition temperatures to be used as a phase change material for cold energy storage and transport. The mass fraction of hydrates in the semi-clathrate hydrate slurry is a key parameter determining the cold carrying capacity and flow properties. We developed a new experimental methodology based on electrical resistivity to quantify the hydrate fraction in semi-clathrate hydrate slurry during hydrate formation. Relationship between electrical resistivity and hydrate fraction of semi-clathrate hydrate slurry was established based on Bruggeman's effective-medium approximation. After validation, this method was employed to quantitatively investigate the effect of temperature on TBAB hydrate formation from 20 wt% TBAB/water system. As the temperature was lowered from 278.2 K to 274.2 K, the induction time was reduced by 97.8% and the hydrate growth rate was enhanced by over 2.5 times. At 274.2 K and 276.2 K, type A hydrates were preferentially formed followed by a structural transition to type B. At 278.2 K, only type A hydrates were observed. Furthermore, given an appropriate concentration, amino acid L-tryptophan was identified to be a good kinetic promoter for TBAB hydrate formation. The presence of 500 ppm L-tryptophan reduced the induction time by 60% and boost the hydrate growth rate by more than 32%. The electrical resistivity-based method developed in this work has shown simplicity, low cost, high accuracy, and repeatability. It would enable precise investigation of semi-clathrate hydrate kinetics in the future for cold energy applications and beyond. [ABSTRACT FROM AUTHOR]

[Display omitted] • Delamination and the electric field induced by clay particle shortens induction time. • Delayed growth kinetics observed in clay suspension with increasing mass fraction. • Water migration and clay agglomeration yielded the stratification of CO 2 hydrate and clay layer. • Heterogeneous spatial distribution of CO 2 hydrate observed in formation and dissociation. Hydrate-based CO 2 sequestration in marine sediments has emerged as a novel sustainable technology for long-term and stable CO 2 sequestration. However, the role of clay minerals in CO 2 hydrate formation and dissociation in clay-rich sediments, which are widely distributed in the South China Sea, remains controversial due to a lack of experimental evidence. This study investigates the effect of a representative clay mineral, sodium montmorillonite (Na-MMT), on the nucleation and growth kinetics of CO 2 hydrate in suspensions with a msass fraction below 20.0 wt%. The kinetic experiments reveal that Na-MMT significantly reduces the induction time due to the additional nucleation sites provided by the delamination of clay particles and the induced surface electric field. While the average growth rate of CO 2 hydrate is reduced by ∼72 % for Na-MMT mass fraction above 5.0 wt%. Morphologically, hydrate-clay stratification and gas-tunneling behaviors were observed, providing explanations for the retarded kinetics. The mass transfer of CO 2 from the gas phase to the liquid phase is impeded by the high viscosity of the suspension and the clay-induced strongly-polarized water layer, which retards the overall kinetics of CO 2 hydrate formation. Upon thermal stimulation, partial CO 2 hydrate dissociation was observed within the pure CO 2 hydrate stability region for 10.0 wt% Na-MMT suspension, indicating a possible impact of Na-MMT on CO 2 hydrate thermodynamics. Moreover, the addition of Na-MMT clay promotes CO 2 hydrate dissociation kinetics significantly. This study provides fundamental insights into the interaction between Na-MMT clay and CO 2 hydrate, offering new perspectives for designing effective strategies for CO 2 sequestration in abundant clay-rich marine sediments. [ABSTRACT FROM AUTHOR]

Natural gas hydrate is a potentially vast energy resource for the future. However, the fundamental behavior of hydrate dissociation during energy recovery is not fully understood due to the complex interplay of phase change and multiphase flow within porous media. In this study, the effect of horizontal wellbore incorporation on the simultaneous gas and water production during the dissociation of methane hydrates in sandy sediment (0.1–0.5 mm) was investigated. A horizontal perforated wellbore was incorporated within water saturated hydrate bearing sediments of 40% hydrate, 55% aqueous and 5% gaseous phase saturation to mimic marine hydrate sediments, and the gas and water production behavior from horizontal wellbore (HW) was compared with the base case (without well) at 3 bottom hole pressures (BHPs) of 3.5, 4.0, and 4.5 MPa under a constant surrounding temperature of 281.5 K. The evolution of temperature across 12 measured locations within the 1 L sediment demonstrated the significant effect of horizontal wellbore incorporation on heat transfer within sediment. Through the incorporation of horizontal wellbore, a continuous production of gas was observed for an extended period of time as compared to the base cases without a well. The resulting cumulative gas production was enhanced by 5.5–10% at various BHPs; whereas the cumulative water production was significantly reduced by 30.8–36.9% at different BHPs from the base cases. By estimating the percentage of hydrate dissociated, it was found that the incorporation of horizontal wellbore in the current apparatus caused a slower hydrate dissociation, as reflected by a longer time to dissociate 50% ( t 50, h ) and 90% ( t 90, h ) of the hydrates. This study demonstrates the potential of horizontal wellbore incorporation to simultaneously enhance gas production and reduce water production, unveiling a future direction in optimizing gas recovery from hydrate reservoirs through innovative wellbore design, configurations and well placement strategies. [ABSTRACT FROM AUTHOR]