Underground gas storage (UGS) into aquifers causes a limited dissolution of gas into the water at the gas-water interface. This phenomenon was characterized and quantified in a study carried out at a UGS site in an aquifer in the Parisian Basin (France).
The study methodology consisted of simulation of water and gas phase equilibrium and comparison of the results with in-situ measurements.
Reliable downhole gas/water holdup data were obtained by modifying a wireline tool based on optical refraction, discriminating gas from liquids and deriving a direct gas holdup. The modified optical tool was combined with an inline spinner and pressure and temperature sensors to allow an optimal evaluation of the zones of interest. Data were acquired in a monitoring well in flowing conditions (25 m3/day water). The survey was recorded from surface down to the producing water interval, revealing gas bubbles freeing from solution only at shallow depth, above 47 m.
Water was also sampled at reservoir conditions with a dedicated wireline tool. The samples show stable concentrations of dissolved gas over time, with methane as the prevalent dissolved gas.
Phase equilibrium was calculated at multiple depths using different thermodynamic equations of state and models. Results from PSRK and MHV2 models, including nucleation overpressure effects, fit well with the acquired data.
Thanks to the innovative logging tool and procedure, the consistency between the acquired and simulated data and the results of the equilibrium models, there is enhanced confidence in the thermodynamic modelling for UGS. The results from this analysis can be now integrated in a reservoir simulator to model the gas/water phase exchanges with a better accuracy.
This workflow can also be applied to other UGS fields for water and gas equilibrium modelling.
Underground gas storage (UGS) into aquifers causes a limited dissolution of gas into the water at the gas-water interface. A study was carried out for the characterization and the quantification of the phenomenon at a UGS site in an aquifer. In-situ measurements of the gas/water holdups were made in a monitoring well, with water samples collected at reservoir depth and along the well using a wireline down-hole measurement technique. The in-situ measurements allowed the validation of a theoretical thermodynamic model of dissolution.
Drill-in fluid systems have been utilized in Congo for several decades to meet the drilling and completion goals for various operators. Both engineered water base muds (WBMs) as well as invert emulsion fluids (IEFs) have been utilized as drill-in fluids with the main focus being on mitigating formation damage and/or providing a filtercake that can be remediated through a post well treatment. Rarely has the engineering of a drill-in fluid taken into consideration the reduction logistics costs and optimizing drilling parameters. By switching from a standard invert emulsion drill-in fluid (IEDF), that included organophilic clay, to the use of a clay-free invert emulsion drill-in fluid (CF-IEDF), the drilling operation realized an overall reduction in logistics; a reduction in volume of fluid and material utilized, and along with higher rate of penetration (ROP) due to lower ECDs.
Emergency Response Plans are used by any Company to protect human lives, the surrounding environment and the facility itself. For what concerns offshore platforms, with the enactment of the European Offshore Directive it has become more and more important to perform the classification of all the possible risks, by identifying the hazards, in order to have a better understanding of all the emergency scenarios to be dealt with to effectively manage the interventions.
According to the client’s requirements, and after having carried out the respective surveys, the existing risk analyses (Hazop) were studied along with all the possible scenarios to be considered; these focused also on the availability of specific equipment or on emergency conditions related to the activities performed in the site.
With reference to this specific approach, emergency plans have been developed for platforms, gas plants and offices, by updating and/or arranging the layouts of the escape routes and fire-fighting equipment.
All the reports of the developed Emergency Plans are divided into three parts: the first part shows a general description of the site; the second part analyses all the possible scenarios, focusing on their impacts and mitigation actions; the third part refers to the description of the company’s organization, the professional roles within the site (related to the emergency situations) and the actions to be undertaken to face each emergency scenario taken into account.
Following the Deepwater Horizon incident in the Gulf of Mexico in April 2010, The European Union demonstrated the willingness of reviewing the rules relating to the hydrocarbon sector with the ultimate aim of improving safety of all Member States. In June 2013, the European Commission published the European Offshore Directive [ref.1]. The objective of this Directive is to reduce as far as possible the occurrence of major accidents related to offshore oil and gas operations and to limit their consequences.
The challenges that the oil and gas industry is currently facing, in terms of continuous cash constraint issues and a prolonged period of volatile and relatively low oil prices, have pushed operators and suppliers to seek new and cost effective technologies, in order to maximize hydrocarbon recovery for producing fields and reduce investments needed for new developments. Specifically for offshore fields located in remote areas and at long step-out, several issues have to be solved, ranging from pipeline cost and flow assurance methodologies to control and power supply. This presentation will focus on the latest developments in Aker Solutions portfolio of processing and power transmission technologies for long step-out subsea applications, targeting to reduce field development costs and minimize related risks. By leveraging the operational experience from recent projects and a close cooperation across the supply-chain with key technology owners, a broad range of new system concepts and technologies have been developed, from optimized subsea compression systems to AC power transmission. Results from the qualification work and testing for some of these technologies will be presented.
Constant bottom hole pressure (CBHP) is one of the techniques used for implementing managed pressure drilling (MPD) mode. It has been introduced to the industry since few years. It aims to provide safe drilling operations, decrease excessive mud costs by reducing lost circulation and preventing well kicks, decrease rig costs by reducing drilling problems including stuck pipe, and non-productive time (NPT). It used especially in drilling wells with a narrow mud window between pore pressure and fracture pressure gradients where selection of the mud properties and drilling techniques in such narrow windows are considered a high challenge. Its application used to reduce the effect of circulating friction loss or equivalent circulating density (ECD) by controlling the annular frictional pressure losses or using continuous circulating system. An additional circulating friction to hydrostatic head can result in formation fracture in drilling or circulation operations, also when stopping circulation the hydrostatic pressure could lies below the formation pore pressure. CBHP could be achieved using the following techniques: 1) Application of Backpressure (ABP), and 2) Continuous Circulation.
This paper is devoted to show the tools used to achieve continuous circulation and the candidates of implementing such technique. The paper provides a case study that illustrates how continues circulation used to enhance the casing design and the mud program. It also illustrates the economic benefits using a cost analysis of the phases that used ENI's circulating device (E-CD™ system) by comparing between conventional drilling techniques and Constant bottom hole pressure -continuous circulation- applications in wells drilled in TEMSAH Field.
Continuous circulation is considered one of the methods used to achieve Continuous bottom hole pressure CBHP through controlling the effect of circulating friction loss or equivalent circulating density (ECD). Continuous circulation could be applied using E-CD™ system (ENI's circulating device), Continuous circulating valve (CCV) and Continuous Circulation System (CCS).
In recent years’ helium detection and analysis in real-time while drilling at wellsite has been gaining interest in the oil and gas industry. The quantification of this noble gas from drilling mud could provide interesting insights thanks to its peculiar generation process and because of its correlation in detecting open micro-fractures, faults, and more in general permeability patterns. The presence of helium in the reservoir could be associated to organic matter presence and to good sealing properties of the cap rock, being the atomic size of helium the smallest amongst the other gases and its leaking properties the highest ones. The study has been focusing on the advantage of having real-time wellsite logs, compared to laboratory tests, thanks to the possibility of having a higher depth resolution of analyses and the most accurate gas composition. A comparison of performances at wellsite of two analytical techniques dedicated to helium quantification will be illustrated: μGC (TCD detector) and mass spectrometer (single quadrupole detector). Helium levels can be used in conventional reservoir characterization, where helium peaks and its concentration variations have been used to infer proper fluid identification, i.e. gas, oil or water, and in the evaluation of separation between two geological sequences. A detailed view of the use of helium in unconventional wells will be illustrated; good agreement of the helium traces with the light hydrocarbons has been highlighted, in accordance to lithologic changes as well. In other cases, the helium concentration has been used to build permeability patterns.
Noble gases are precious markers for natural fluid characterization. Most of the interest in this topic has been driven by many academic studies on isotopic ratios of noble gases. The common feature amongst all these gases is their chemical inertness; as they are generated and only physical processes govern their migration and isotopic fractionation. This could be used to study migration pathways of hydrocarbons and to trace the mixing processes that a certain formation has passed through (isotopic fractionation).
Floating Facilities are widely spread by the time, and production from those Units is becoming more and more relevant in the oil & gas market. Since the start up of "Agip Milano" in 1978, Eni has put continuous effort to grow in this contest, claiming today a fleet of an important variety of typologies and peculiarity of characteristics. Experience has been matured, following the change in context and background conditions, supporting the transformation of Floating Facilities from Units conceived to exploit marginal, near to shore fields with low complexity, in Units fit to exploit large and complex fields. Progress in deep water exploration and drilling over the past ten-plus years has also yielded a large number of new discoveries, definitely to be developed through Floating Units. Current projects entail increasing complexity of production environment and highly sophisticated and technologically advanced production systems, and, now more than ever, a solid and efficient O&M management philosophy is perceived as a fundamental need. For this reason, an incisive, efficient and correct approach to "Readiness for Operations" helps to improve overall safety and to reduce operating costs. Eni consolidated process of "Operations Readiness and Assurance", as applied to Floating Facilities, with full involvement of O&M Contractor, will be described in this paper taking advantage of several examples.
In order to minimize risk of fatigue failure of pipes and other structural components, a subsea condition monitoring or inspection tool may be required to keep production at a safe level. Reliable and efficient condition monitoring solutions are increasingly important as a growing body of production and processing assets are moved subsea. This paper will illustrate the use of an efficient condition monitoring system that can also be used for one-shot inspection, with smart installation method and data retrieval solution – as well as data from a field case.
Vibration monitoring can be performed using clamp-on and retrofit instrumentation and even included in instruments that also perform other tasks such as particle monitoring, leak detection, or corrosion/erosion monitoring. The combination of vibrometry and passive acoustic noise detection at ultrasonic frequencies holds an interesting potential for condition monitoring of critical equipment.
The subsea sensors can either be installed as permanent on-line condition monitors, or deployed at intervals to detect changes over time in vibrational and acoustic signatures. The latter is of particular interest in cases where provision of power and communication for retrofit instrumentation is costly, and where data from great numbers of inspection points are desirable.
Subsea testing of a vibration inspection concept is carried out early 2013, using battery operated instruments in combination with a novel quick-mount solution for ROV deployment on subsea structures. The instrumentation is placed in standard ROV buckets at measurement points of interest and left at each position for a period of choice, ranging from hours to months. Returning to the same site, vibration and noise measurements can be compared to records from earlier inspections. The concept, preliminary results, and further possibilities for reliable and efficient condition monitoring and inspection are presented.
INTRODUCTION Statistics tells us that 21% of all topside pipework failure in the UK sector is due to vibration-induced fatigue, whilst erosion and corrosion stands for 13% (Figure 1). This is not directly comparable with the subsea world. Still, we now know that aging subsea pipework and structures suffer from fatigue, in many cases caused by vibration. The number one cause of vibration-induced fatigue is flow line induced vibration (FIV). Advanced simulation and modelling are often used when designing subsea structures and subsea pipework to ensure that the design minimizes the risk of harmful vibration occurring. Simulation and modelling have become very accurate but does not always fully reflect real conditions due to the complexity of the pipework in combination with the unpredictability of multiphase flow regimes. Therefore, these models are usually quite conservative, with a significant safety margin built in. In some cases, this may lead to a “permitted production rate” that is less than is safely possible. Installation of permanent or temporary vibration monitoring is the only way to be sure what the actual state is. Data from instrumentation is valuable for several reasons.
Bartelucci, P. (Eni S.p.A.) | Borghi, M. (Eni S.p.A.) | Crottini, A. (Eni S.p.A.) | Galli, G. (Eni S.p.A.) | Pirrone, M. (Eni S.p.A.) | Rizzo, G. (Eni S.p.A.) | Nardiello, R. (Baker Hughes Inc. ) | Chace, D. (Baker Hughes Inc. ) | Kim, Y. (Baker Hughes Inc. ) | Zhang, Q. (Baker Hughes Inc. )
This paper presents a cased hole methodology for gas density and pressure calculation to quantify the gas depressurization in mature gas fields by use of Pulsed Neutron technology. The approach is based on an advanced interpretation of gas saturation behind casing and utilizes Monte Carlo reservoir characterization models based on different gas density responses.
The field application refers to an onshore multi-layer sand reservoir in the eastern Pianura Padana Basin producing biogenic gas since 1971. A strong decline of static bottom hole pressure (SBHP) has been recorded during the field life. The pressure drop is not constant and/or equal across the field gas levels and it may vary a lot between them. In many cases, the pressure of the single layers cannot be measured since two or more layers are completed to the same casing string.
The following proposed methodology allowed to quantify the different depletion degree of the main field levels for reservoir management and production optimization purposes. The first step of the analysis is to calculate the current reservoir gas saturation using commercial pulsed neutron ratio-based measurements. The following pressure depletion analysis could be applied if the original water saturation is unchanged and only a pressure drop has occurred. Capture Cross Section (Sigma) analysis is relatively insensitive to pressure depletion, but it can be used with confidence to confirm that the original water saturation has not changed. Assuming unchanged the open hole reservoir conditions in terms of reservoir saturation and pressure, if the current ratio derived gas saturation excesses the open hole saturation, then the gas density is iteratively reduced and the calculation repeated using new modeled responses. Depleted gas density and related reservoir pressure are finally determined when calculated cased hole gas saturation matches the original open hole gas saturation.
The current industrial standards adopted to simulate the liquid particle erosion phenomena are based on 1-D equations prescribed by the API114E, which computes the erosion limit velocity related to different materials considered. Therefore, this method relies on simplified models and empirical correlations, validated by experimental data, but characterized by the requirements of an over-design margin factor, to face the large uncertainty intrinsic with the physical phenomenon.
In this paper, two CFD multiphase procedures able to simulate the liquid erosion effect in continuous gas phase are presented and applied to support the start-up operations of a new gas/condensate field located offshore in Central America. Indeed, the insurgence of dangerous liquid/gas erosions phenomena, can affect significantly the platform production manifold before the sea line.
The procedures are based on two different approaches and tools: the Eulerian/Eulerian implemented on OpenFOAM and the Lagrangian/Eulerian investigated with Fluent. In both cases, the flux is considered fully dispersed, and a new algorithm that evaluates and sets the liquid droplet diameter as a function of Webber number, flow regime and geometry variations has been included.
In the first case both liquid and gas are modelled using the Eulerian framework, applying an innovative application devolved in OpenFOAM for two-phase dynamics. The critical erosion velocity is computed along with the superficial pressure and consequently the shear stress on the wall. This allows to apply an experimental model (from literature) able to estimate the rate of erosion to the Eulerian solver. On the other hand, the second approach implements a coupled Lagrangian (liquid) Eulerian (gas) framework. In this case the dispersed phase is not able to penetrate the continuous one, but it is absorbed by the wall after the erosive impact. The same reference model for erosion rate evaluation has been adopted to tune the tools already offered by Fluent. The comparison of the results obtained by both CFD analyseis and industrial standards is reported and within this work. Final recommendations to be applied on field for start-up operations have been summarized.
The CFD procedures developed seems to offer the possibility to gain a deeper understanding of erosional physical phenomenon effects: erosion rate, critical velocity, shear stress and phases distribution. This gives the capability to reduce the uncertainty related to the industrial standards, maintaining the computational efforts for the Oil and Gas time scale competitive and optimizing the operating conditions during the entire life of the asset.