Gravel Pack Research Articles

Investigating the Impact of Sieve Analysis on the Choice of Gravel Pack Design for Wells in Unconsolidated Sandstone Formations in the Niger Delta

Sand production is major problem for the oil and gas industry and solutions to this problem is a continuous process as new challenges arise with time. Various sand control methods have been proposed for tackling the sand production challenge, and research and experience have shown that the use of mechanical sand control methods are more suitable, with gravel packing being the most effective. Gravel packs are proven to be an effective mechanical sand control technique, and a good gravel pack completion design is of great importance to exclude sand from the wellbore while enhancing well productivity. Implementation of sand control by gravel packing in the Niger Delta is usually found to require importation of commercial gravel for the purpose of sand control which is a challenge in terms of high purchasing and transportation costs with import taxes. A solution is presented in this study which involves sourcing for gravel locally and investigating its suitability for sand control by gravel packing. Locally sourced gravel was compared with commercial gravel using sieve analysis and results showed that the locally sourced gravel closely met the requirements of the commercial gravel depicted by slot widths that are close to that obtained by the commercial gravel. Based on the results of this study, favorable performance is expected when locally sourced gravel is used for sand control by gravel packing in unconsolidated formations in the Niger Delta. It is recommended to source for different gravel types from different locations and evaluate using sieve analysis and Laser Particle Size Distribution Analysis to determine suitable gravel types for these type of formations.

Experimental and Numerical Analysis of Particle Migration and Patterning Behavior in a Gravel Pack

Due to its long lifespan and high sand-removal efficiency, gravel packing is one of the most applied sand control methods during the recovery of reservoirs with sanding problems. The blockage and retention of injected sand in a gravel pack is a complex process affected by multiple mechanisms. The majority of existing studies based on the phenomenological deep bed filtration (DBF) theory focused on the gravel pack’s overall permeability damage and failed to obtain the inner-pore particle distribution pattern. In this work, experiments and simulations were carried out to reveal the particle distribution in a gravel pack during flooding. In particular, through real-time monitoring of particle migration, the penetration depth and distribution pattern of invaded particles with different gravel-sand particle ratios, fluid viscosities and injection rates could be determined. By simplifying each unit bed element (UBE) into a pore-throat structure with four tunnels (two horizontals for discharge and two verticals for sedimentation), a new network simulation method, which combines deep bed filtration with a particle trajectory model, was implemented. Cross comparison of experimental and numerical results demonstrates the validity and accuracy of the model.

Analiza performansi polimera hidroksietil celuloze (HEC) kao sredstva za želiranje u tečnoj formulaciji nosača šljunka za kontrolu peska u bunarima za proizvodnju ugljovodonika

This study considers the performance of 40ppt and 60ppt hydroxyethyl cellulose (HEC) polymer used as a gelling agent in the formulation of carrier fluids for gravel pack transport in sand control operations in oil and gas wells. The gravel pack carrier fluid was prepared by adding adequate amounts of sodium persulfate (SP) used as gel breaker, Fe-2 used as an iron control agent, KCL brine as mixed fluid, K-35 used as pH buffer, BE-6, and BE-35 used as biocides, HEC used as a gelling agent, and distilled water. The effects of temperature, gel loading, and breaker fluid concentration on the rheology, gel break time, and sand settling of the formulated HEC carrier fluid were considered. The results showed that shear stress, plastic viscosity and yield point and consistency factor decreased with an increase in bottomhole temperature for both 40ppt and 60ppt HEC gels. Furthermore, flow behaviour index was observed to be within the range of 0.45±0.1 40ppt and 0.5±0.04 for 60ppt HEC of gel loading, respectively and showing shear-thinning characteristics. Good gravel settling was observed for the HEC gels when in contact with gravel, addition of breaker fluid greatly improved the sand/gravel suspension for 40ppt and 60ppt gel loadings. Gel break time of the HEC gel increased with increasing gel loading, and at higher breaker fluid concentrations, HEC gel degradation becomes more critical as temperature increases. The results highlight the adequate performance of HEC polymer as gravel pack fluid in sand control operation.

Gravel padding filters for combating sandblasting in wells

This paper presents an analysis the technology for creating an artificial gravel pack behind the casing in the near-wellbore part of the formation in producing oil and gas wells. Gravel-embedding filter is not only a special device installed in the well to clean the fluid extracted from the formation of sand and other foreign impurities, but also the use of gravel in conjunction with the filter in order to retain the formation sand at the site of its occurrence. Wells are equipped with gravel filters when completing them in formations represented by medium to fine grained and silty sands. The desiccant layouts of gravel stuffing filters on lightly cemented sandstones are presented in the work show high efficiency, as they prevent the removal of sand during the well operation. Creating an artificial gravel pack is an effective way to prevent sand from entering the well.

Downhole Sand Control Applied for High-Rate Gas Completions in Deepwater Malaysia

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 31413, “Applying Downhole Sand Control for High-Rate Gas Completions in Deepwater Malaysia,” by Elvy Jose Samuel, SPE, Mohd Faizal Yusoff, and Phil Bee, PTTEP, et al. The paper has not been peer reviewed. Copyright 2022 Offshore Technology Conference. Reproduced by permission. _ Designing and delivering a successful completion in a subsea high-rate gas deepwater environment is a great challenge in upstream field development. The complete paper covers the sand-control design and execution techniques applied to four high-rate gas wells in the operator’s Block H development in the deepwater region of Sabah offshore Malaysia in 2020 and 2021. Field Background PTTEP’s Block H gas development is a multifield phased subsea development designed to deliver gas to Petronas’ floating liquefied natural gas (FLNG) project known as PFLNG2. The Block H field is in the South China Sea in water depths between 1150 and 1400 m. The first phase (Phase 1A) of the project was executed in four wells between the Rotan (three wells) and Buluh (one well) fields in the midsection of the Block H development. The reservoirs completed in Phase 1A were deepwater slope turbidite sands deposited during the Late Miocene and contain high net-to-gross reservoirs. Based on evidence from sonic logs and rock-mechanics testing performed on rotary side-wall cores and fullbore cores, all targeted reservoirs required robust sand control. Openhole gravel packing (OHGP) was chosen as the recommended sand-control technique for the high-rate gas application, and the four wells were drilled nearly vertically, with high water standoff height as a mitigation against early water coning. The drilling and completion operations were completed in a batch completion strategy in which all top holes were drilled to the top of the targeted reservoir, followed by the batch completion of all wells’ lower completion phase, then the batch upper completion and well cleanups. The wells were placed on production in Q1 2021 to PFLNG2, achieving the targeted rates per well of 80 MMscf/D solids-free.

Measuring the Effect of Pack Shape on Gravel’s Pore Characteristics and Permeability Using X-ray Diffraction Computed Tomography

Particle shape is one of the critical parameter factors that affect gravel’s pore structure and permeability. However, few studies have considered its effects on engineering applications due to the difficulty of conducting laboratory tests. To overcome these difficulties, new methods of estimating the gravel pack shape that involve manual work and measuring the surface area of particles and pores based on support vector machine segmentation and the reconstruction of X-ray diffraction computed tomography (CT) images were proposed. Under the same conditions, CT tests were carried out on gravel packs and two other regular-shaped particle packs to investigate the influence of particle shape on the fractal dimension of gravel’s pore–particle interface and the specific surface area of the pore network. Additionally, permeability tests were performed to study the effect of particle shape on gravel’s hydraulic conductivity. The results showed that a gravel pack with a larger aspect ratio and a smaller roundness had a larger specific pore network surface area and a more complex pore structure, leading to lower permeability. This kind of gravel had a more significant length, quantity, and tortuosity of the seepage path when seepage occurred in a two-dimensional seepage field simulation. Therefore, we suggest that the filter materials of hydraulic projects should preferably use blasting gravel with a larger aspect ratio and smaller roundness to achieve better anti-seepage properties. In addition, projects can increase pores’ specific surface area using our method as a control factor in filter construction.

Evaluation the feasibility of using clinoptilolite as a gravel pack in water wells for removal of lead from contaminated groundwater.

The ability of clinoptilolite zeolite as a filter in water wells to remove lead from polluted groundwater was tested in batch and fixed-bed column experiments. XRF, XRD, SEM, and BET were used to characterize the zeolite. Because of the pH variation in groundwater, batch experiments were performed at pH = 6, 7, and 8, with the highest removal efficiency (84.2%) at pH = 6 and 298K within 90min. The Freundlich model accurately predicted metal ion adsorption behavior and indicated a multilayer adsorption of Pb(II) molecules on the inhomogeneous surface of clinoptilolite. The best-fitting kinetic model for clinoptilolite is the pseudo-second order equation, highlighting that the rate of adsorption is dependent on absorbent capacity. Next, the effect of flow rate, bed depth, and grain size of clinoptilolite on lead removal was investigated in column experiments at an initial concentration of 450mg pb/L. The highest removal efficiency was achieved in column experiments with a flow rate of 1mL/min, a bed height of 10cm, and a grain size of 0.6 to 0.8mm. Breakthrough curves were predicted by the Thomas and Yoon-Nelson models, with excellent agreement with the corresponding experimental data. This research will be used to develop a new in situ remedial approach for removing lead from polluted groundwater.

Deep learning long short-term memory combined with discrete element method for porosity prediction in gravel-bed rivers

The porosity of gravel riverbed material often is an essential parameter to estimate the sediment transport rate, groundwater-river flow interaction, river ecosystem, and fluvial geomorphology. Current methods of porosity estimation are time-consuming in simulation. To evaluate the relation between porosity and grain size distribution (GSD), this study proposed a hybrid model of deep learning Long Short-Term Memory (LSTM) combined with the Discrete Element Method (DEM). The DEM is applied to model the packing pattern of gravel-bed structure and fine sediment infiltration processes in three-dimensional (3D) space. The combined approaches for porosity calculation enable the porosity to be determined through real time images, fast labeling to be applied, and validation to be done. DEM outputs based on the porosity dataset were utilized to develop the deep learning LSTM model for predicting bed porosity based on the GSD. The simulation results validated with the experimental data then segregated into 800 cross sections along the vertical direction of gravel pack. Two DEM packing cases, i.e., clogging and penetration are tested to predict the porosity. The LSTM model performance measures for porosity estimation along the z-direction are the coefficient of determination (R2), root mean squared error (RMSE), and mean absolute error (MAE) with values of 0.99, 0.01, and 0.01 respectively, which is better than the values obtained for the Clogging case which are 0.71, 0.14, and 0.03, respectively. The use of the LSTM in combination with the DEM model yields satisfactory results in a less complex gravel pack DEM setup, suggesting that it could be a viable alternative to minimize the simulation time and provide a robust tool for gravel riverbed porosity prediction. The simulated results showed that the hybrid model of the LSTM combined with the DEM is reliable and accurate in porosity prediction in gravel-bed river test samples.

A Novel Approach to Predict Sand Production Rate through Gravel Packs in Unconsolidated Sediment Applying the Theory of Free Fall Arch

Summary Sand production can yield severe operational issues during natural gas hydrate (NGH) exploitation. As a prerequisite for effective sand control design, a reliable simulation approach is required to predict sand production rate of the unconsolidated sediment after hydrate decomposition. In the present study, a quantitative model to predict fluid-driven sand discharge rate has been proposed by assuming an imaginary free fall arch (FFA) region at the gravel pack interface. Through integrating the FFA particle discharge model, critical remigration velocity model, and sand erosion model, a novel simulation approach is developed to determine the time-dependent permeability change of the sanding sediment during depressurization-induced hydrate exploitation. The numerical model was verified through comparison against the flooding experiments with both single opening and gravel pack. A sensitivity analysis was carried out to study parameters (such as packed gravel size, sand particle size, opening blockage, and hydrate reformation) that may affect the sanding rate and permeability distribution within the unconsolidated sediment as well. By utilizing the simulation approach proposed in this paper, the sand intrusion within the gravel pack and the permeability variation of the unconsolidated sediment can be obtained in a computationally efficient way, which is of significance in sand control design and potential geological risk identification during hydrate exploitation.

A novel multi-path sand-control screen and its application in gravel packing of deepwater horizontal gas wells

Gravel packing is a promising sand control method for natural gas wells in deepwater environments. However, premature screenout, wellbore shrinkage, and packer installationlimit gravel packing efficiency in long-reach horizontal wells. In this paper, we introduce a novel multi-path screen that provides alternative pathways once the circulating annulus is blocked. The basic geometric parameters of the screen are given first. Then, the frictional pressure loss in each circulating unit during packing is evaluated. Finally, the application of this screen in a long-reach horizontal well in the northern South China Sea is discussed. The application results demonstrate the applicability of multi-path screens in complex downhole completion conditions. The multi-path screen described here may widen the application ranges of gravel packing techniques to meet the exploitation demand for unconventional natural gas resources, such as marine natural gas hydrate.

Experimental study on sand control gravel particle gradation optimization in mud hydrate reservoir

Sand production significantly influences the safety and stability of gas hydrate exploitation in reservoirs with high mud content. Gravel packing is an effective method for sand control. The median grain size ratio (D50/d50) values and fine particle content of gravel pack are important factors in sand control during natural gas hydrate exploitation. This paper focuses on the sand blocking effect and permeability characteristics of different grades of gravel. The sand retention test was carried out on four samples with different ratios. The optimal D50/d50 value and fine particle content for gas hydrate production were obtained. A laser particle size analyzer and geotechnical test found the reservoir and gravel layer pore structure change. The results show that the optimal GSR was 24.5, and the optimal fine particle content was about 38%. The permeability decline of the gravel layer occurs in the early stage of production, and the fine particles in the gravel will slow down the degree of seepage damage. For gravel with the same particle size range and different median particle sizes, it has little effect on sand control accuracy but mainly on permeability. The research in this paper can provide a reference for selecting sand control gravel for natural gas exploitation in marine areas.

Experimental Study on the Permeability Damage Mechanism of Gravel Pack Sand Control Medium in Mud Hydrate Reservoirs

Yu, L.; Han, Z.; He, J., and Li, G., 2022. Experimental study on the permeability damage mechanism of gravel pack sand control medium in mud hydrate reservoirs. Journal of Coastal Research, 38(6), 1104–1115. Coconut Creek (Florida), ISSN 0749-0208. The high argillaceous gas hydrate reservoir contains high silt and fine sand content. During the mining process, the fine silt sand will cause blockage of the gravel sand control medium, resulting in reduced medium permeability, that is, penetration damage. Penetration damage will reduce productivity and affect the long-term effectiveness of gravel. For the penetration damage problem of gravel sand control medium, the sand blocking simulation experiment of different reservoir water content, experimental pressure, and gravel specifications were carried out by self-developed sand blocking experiment system. A laser particle size analyzer and electron microscope were used to measure and observe the deposition of sand particles in the upper, middle, and lower layers of gravel layer after the sand retention experiment. The law of permeation damage and the mechanism of media permeation damage were summarized. The research results show that the blockage of sand control media can be divided into four stages: the beginning of blockage, the intensification of blockage, the dredging of blockage, and the balance of blockage. Reservoir water content, experimental pressure, and gravel size all influence permeability damage of gravel. The primary and secondary relationship of the influence of these factors on permeability damage is gravel size, experimental pressure, and reservoir water content. The pressure mainly affects the invasion depth of reservoir sand. The reservoir water content mainly affects the degree of permeability damage. The optimum particle size median ratio D50/d50 is about 25, and the medium has strong antipermeability damage ability and good sand retaining effect.

Simulation and application analysis of gravel packing in deepwater HT/HP wells

AbstractGravel packing is one of the main sand control methods for deep‐water high‐temperature and high‐pressure (HT/HP) reservoirs. According to the specific characteristics of deep‐water HT/HP and multichannel, considering the influence of slurry flowing through long‐distance multichannel and the slurry temperature alternation along the flow path, based on α–β wave packing theory, a coupling model of gravel packing in deep‐water HT/HP horizontal wells is established. The packing simulation algorithm and calculation process are designed to realize the gravel packing temperature pressure simulation and multistage refined friction calculation of deep‐water HT/HP horizontal wells. The influence of each packing parameter on the packing process is fully studied. Furthermore, the application simulation of the A10H well of the South China Sea deepwater HP well is carried out. The simulation results show that in the slurry injection stage and α wave packing stage, the packing pressure is low and the residual pressure window is large. In the β wave packing stage, the packing pressure increases rapidly, the residual pressure window shrinks rapidly, and finally, at the end of β wave packing, the residual pressure window becomes narrow. The viscosity of carrier fluid has a significant impact on the pressure window of packing operation. For the design pump rate of 5.6 bpm, the packing cannot be completed with 5.0 cp viscosity carrier fluid. For the carrier fluid with high viscosity, the multi‐β wave packing technique of pump reduction control pressure at the end of the β wave packing stage is used, and this process is simulated in this paper. Considering three constraints: not sand packed in the drilling string, without premature bridging in the α wave packing stage, and α and β wave packing pressure control conditions, the safe range of pump rate is determined under different operation safety margin conditions, which can provide technical support for on‐site operation.

INV-FLOW: New Possibilities to Evaluate the Technical Condition and Function of Extraction Wells

The declining supply of available groundwater resources is increasing the importance of extraction wells. To maximize the yield of extraction wells, the operators do not always respect the sustainable use of groundwater resources. These efforts can affect water quality and impact the service life of an extraction well, mainly through the clogging process. As part of the INV-FLOW project, an apparatus for evaluating the functionality of an extraction well by measuring the vertical water flow through its screen and filter was designed and tested. The apparatus consists of two electromagnetic induction flowmeters, two pneumatic seals, and a pump with the possibility of regulation. After an initial laboratory verification of the fundamental concept, the apparatus was successfully tested in real conditions. Two extraction wells, HJ-3 and HJ-4, intended for water supply to an agricultural production plant, were measured at a pilot site in the Czech Republic using the INV-FLOW apparatus. Although the HJ-3 extraction well is at the end of its service life, the HJ-4 extraction well is a newly installed well. In the new extraction well, HJ-4, a high proportion of water flowing through the gravel pack relative to the total pumping flow (93–97%) was measured using the INV-FLOW apparatus at different pumping rates. In the case of the HJ-3 extraction well, screen and filter clogging contributed significantly to the limited water flow through the gravel pack. In the most affected parts of the extraction well (15–20 m b.g.l.), the proportion of water flowing through the gravel pack relative to the total pumping flow ranged from 10 to 20%. The pilot tests confirmed the functionality of the apparatus and the possibility of using it to evaluate the degree of clogging and incrustation of an extraction well. The pilot tests thus demonstrated the usability of the INV-FLOW apparatus. The extraction well operator can assess the level of clogging or incrustation of the extraction well and decide on the need for the rehabilitation of an extraction well, or the termination of its operation.

Concurrent 10. Presentation for: Collaborating to bring new technology on developments

Presented on Wednesday 18 May: Session 10 Project delivery certainty is a key a success factor for positive business outcomes. Taking on world first applications across multiple delivery streams comes with risk that requires significant risk reduction to meeting business requirements. The Julimar Development completed this successfully across both drilling and completions, and subsea. Reliable multizone completions with robust sand control have traditionally been a challenge in high-rate gas wells. Cased hole stacked gravel packs can leave high mechanical skin, require multiple trips and are complex operations. While Open Hole Gravel Packs (OHGPs) have provided reliable sand control in such wells, multizone applications have been limited due to the tradeoff between effective gravel placement and zonal isolation. Recent developments in technology have enabled reliable gravel placement and complete zonal isolation. The collaboration between Woodside and Subsea 7 has delivered an ‘industry first’ on the Julimar Project, with the completion of an 18″ Corrosion-Resistant Alloy (CRA) gas transmission flowline installed via reel-lay – the largest diameter insulated CRA pipeline ever reeled. For background, most projects have traditionally used the ‘S-Lay’ method for installing pipe in Australia – the reel-lay method is less common. A key benefit of the reel-lay method is it removes thousands of welds from the offshore installation vessel critical path, transferring them onshore into a safer, quality-controlled environment earlier in the schedule. Pipe joints are welded into ‘stalks’ which are then spooled onto purpose-built reel-lay vessels. Woodside and Subsea 7 were able to jointly demonstrate the safety, quality, technical and cost advantages of this innovative but field-proven reeled pipe-lay technology. The 18″ CRA flowline is a tangible example of the performance that can be delivered through early collaborative engagement and strategic investment in technology and is a step change in Australia and the industry. This joint presentation discusses contracting, design, execution and evaluation of technologies on the Julimar Development. It includes the method followed for reel-lay technology selection, engineering development, post project evaluation and the health and safety benefits. The presentation provides both the Operator and Contractor perspectives on the challenges of implementing new technology in developments in Australia. To access the presentation click the link on the right. To read the full paper click here and also here.

Characterization of Sand Production for Clayey-Silt Sediments Conditioned to Hydraulic Slotting and Gravel Packing: Experimental Observations, Theoretical Formulations, and Modeling

Summary In our previous work (Jin et al. 2021), an experimental effort has been made to microscopically observe sand failure, migration within a matrix, invasion toward gravel-packing zones, and production conditioned to the openhole gravel packing, while three sanding patterns (i.e., fractures, wormholes, and fluidized channels) have been identified. The first pattern is associated with an uneven strain-stress effect, while the last two patterns result from liquid seepage. To theoretically reproduce our previous experimental measurements, in this study, the experimental techniques have been further modified and improved to eliminate the associated uneven strain-stress effect by uniformly injecting water into a radial flow vessel. Experimentally, by generating slots near the gravel packing, sand failure dynamics, sand flow paths, and sand production for the clayey-silt sediments can be microscopically observed, geometrically depicted, and volumetrically quantified conditioned to different operational conditions (i.e., no hydraulic slot, single hydraulic slot without proppants, single hydraulic slot with different lengths, and double hydraulic slots with different intersection angles). Theoretically, a wormhole growth model has been proposed to reproduce the sand production for both hydrate-free and hydrate-bearing sandpacks by accounting for a sand failure criterion as well as the porosity and permeability alteration models. Good agreements between the measured and simulated data (i.e., pressure and temperature profiles, cumulative gas and water production, and produced sediment volumes) have been achieved. The experimental results show that hydraulic slotting can be used to not only effectively mitigate the skin effect near a wellbore but also decrease the pressure gradient near the wellbore. In this way, the possibility of sand failure is decreased if a predesigned hydraulic slotting after well completion is deployed. It is revealed that the operational conditions dictate the sand failure patterns, sand production volumes, and sizes of the produced particles. Similar to hydrate dissociation, sand production is also divided into three stages: before dissociation (transport of free particles or weakly consolidated particles), during hydrate dissociation (sand detachment because of the loss of hydrate cohesion and massive water production), and after hydrate dissociation (transport of fully unlocked particles). Furthermore, sensitivity analysis shows that cumulative sediment production and permeability increment are affected by the following strong-to-weak order: intrinsic failure resistance, tortuosity, Kozeny coefficient, and absolute permeability. Also, the breakdown pressure is dominated by absolute permeability, while pressure during the stable stage is mainly dictated by the intrinsic failure resistance, tortuosity, and Kozeny coefficient.

Multiple world first technology applications on Julimar Development Phase 2 – multizone openhole gravel packing with enhanced shunted screens and zonal isolation in high rate gas wells and 18″ reel lay for corrosion resistant alloy (CRA) flowlines

Project delivery certainty is a key success factor for positive business outcomes. Taking on world first applications across multiple delivery streams comes with risk that requires significant risk reduction to meet business requirements. The Julimar Development completed this successfully across both drilling and completions, and subsea. Reliable multizone completions with robust sand control have traditionally been a challenge in high-rate gas wells. Cased hole stacked gravel packs can leave high mechanical skin, require multiple trips and are complex operations. While OpenHole Gravel Packs (OHGPs) have provided reliable sand control in such wells, multizone applications have been limited due to the trade-off between effective gravel placement and zonal isolation. Recent developments in technology have enabled reliable gravel placement and complete zonal isolation. The largest flow line installation by reel lay for corrosion resistant alloy (CRA) flowlines was previously 16″. Increasing this size to 18″ required an in-depth understanding of key risks for the contractor to deliver on the size increase, and for Operator to engineer in risk mitigation. Key areas to understand included vessel capability, new build spool base, engineering methods to support delivery and the Operators role in change management when additional risks are identified, or issues occur. This paper discusses contracting, design, execution and evaluation of technologies on the Julimar Development. It includes methodology followed for both technology selections, engineering development, qualification tests, post project evaluation, lessons learned along with health and safety benefits.

Collaborating to bring new technology on developments

Project delivery certainty is a key a success factor for positive business outcomes. Taking on world first applications across multiple delivery streams comes with risk that requires significant risk reduction to meeting business requirements. The Julimar Development completed this successfully across both drilling and completions, and subsea. Reliable multizone completions with robust sand control have traditionally been a challenge in high-rate gas wells. Cased hole stacked gravel packs can leave high mechanical skin, require multiple trips and are complex operations. While Open Hole Gravel Packs (OHGPs) have provided reliable sand control in such wells, multizone applications have been limited due to the tradeoff between effective gravel placement and zonal isolation. Recent developments in technology have enabled reliable gravel placement and complete zonal isolation. The collaboration between Woodside and Subsea 7 has delivered an ‘industry first’ on the Julimar Project, with the completion of an 18″ Corrosion-Resistant Alloy (CRA) gas transmission flowline installed via reel-lay – the largest diameter insulated CRA pipeline ever reeled. For background, most projects have traditionally used the ‘S-Lay’ method for installing pipe in Australia – the reel-lay method is less common. A key benefit of the reel-lay method is it removes thousands of welds from the offshore installation vessel critical path, transferring them onshore into a safer, quality-controlled environment earlier in the schedule. Pipe joints are welded into ‘stalks’ which are then spooled onto purpose-built reel-lay vessels. Woodside and Subsea 7 were able to jointly demonstrate the safety, quality, technical and cost advantages of this innovative but field-proven reeled pipe-lay technology. The 18″ CRA flowline is a tangible example of the performance that can be delivered through early collaborative engagement and strategic investment in technology and is a step change in Australia and the industry. This joint presentation discusses contracting, design, execution and evaluation of technologies on the Julimar Development. It includes the method followed for reel-lay technology selection, engineering development, post project evaluation and the health and safety benefits. The presentation provides both the Operator and Contractor perspectives on the challenges of implementing new technology in developments in Australia.

Field Testing of a Novel Drilling Technique to Expand Well Diameters at Depth in Unconsolidated Formations.

Larger well diameters allow higher groundwater abstraction rates. But particularly for the construction of wells at greater depth, it may be more cost-efficient to only expand the borehole in the target aquifer. However, current drilling techniques for unconsolidated formations are limited by their expansion factors (<2) and diameters (<1000 mm). Therefore, we developed a new technique aiming to expand borehole diameters at depth in a controlled manner using a low-pressure water jet perpendicular to the drilling direction and extendable by means of a pivoting arm. During a first field test, the borehole diameter was expanded 2.6-fold from 600 to 1570 mm at a depth of 53.5 to 68 m and equipped with a well screen to create an expanded diameter gravel well (EDGW). In keeping with the larger diameter, the volume flux per m screen length was two times higher than conventional 860 mm diameter wells at the site in the subsequent 3year production period. Although borehole clogging was slower on a volumetric basis and similar when normalized to borehole wall area, rehabilitation of particle clogging at the borehole wall was more challenging due to the thickness of the gravel pack. While jetting the entire borehole wall before backfilling holds promise to remove filter cake and thus limit particle clogging, we found that a second borehole (expanded 4.1-fold to 2460 mm) collapsed during jetting. Overall, the EDGW technique has potential to make the use of deeper unconsolidated aquifers economically (more) feasible, although further understanding of the borehole stability and rehabilitation is required to assess its wider applicability.

Step-drawdown tests: linear and nonlinear head loss components

Coefficients B and C of the Jacob (1947) equation, usually derived from step-drawdown tests, are commonly attributed to “aquifer losses” and “well losses”, respectively. This paper analyzes and separates the linear laminar, nonlinear laminar and turbulent losses occurring during flow from an aquifer to a screened well. From this, one can derive a detailed physical meaning for both coefficients. The coefficient B does not contain only aquifer losses but also linear losses from the gravel pack and wellbore skin, if present. Coefficient C contains nonlinear laminar losses from the gravel pack and turbulent losses caused by screen inflow and vertical flow through the screen and casing. In some cases, the turbulent losses are small enough to be omitted. For transient flow at larger times, the changes in linear laminar losses within the aquifer become important. A new, explicit formulation of the Jacob equation was compared to long-duration field step-drawdown tests, three in confined unconsolidated formations and one in a fractured rock aquifer. Jacob C.E. (1947) Drawdown test to determine effective radius of artesian wells. Trans. Am. Soc. Civil Eng. 112:1047–1070.