Annular Flow Modelling and Advanced Well Completions Design Optimisation in Oil Rim Reservoirs

The inflow control device completion has proved to be an effective solution to mitigate water and gas breakthrough and coning problems. One of the major parameters affecting the ICD completion's performance is annular flow, the flow of the fluid in the space between the base pipe and the sand-face. The importance of annular flow on the ICD completion was addressed by many researchers. However, there was lack of an analytical annular flow model to integrate the effect of all parameters important contributing to the annular flow. In this study a comprehensive annular flow modelling and ICD completion design using a reservoir simulation model are presented. The results of the study show that ICD completions mitigate the heel-toe effect which is resulted from an improper well configuration. A sufficiently high strength ICD completion reduces the dependency of the annulus pressure to the flowing pressure along tubing itself i.e. reducing the heel-toe effect. This results in minimising the annular flow even with no need of annular flow isolation (AFI) tools like swellable packers. AFI installation would be less necessary in homogenous reservoirs when an appropriate ICD completion design, which could be determined by the analytical annular flow equations, was used

Estimation of in-situ compositions in lean gas condensate reservoirs

There is a high degree of complexity in both fluid flow and phase-behavior of gas condensate reservoirs during the depletion period due to retrograde condensation. Natural depletion in gas condensate reservoirs results in low condensate recoveries at surface due to in-situ condensation and accumulation of condensate in the reservoir especially in vicinity of wellbore. During reservoir depletion, the overall composition of reservoir fluid varies and becomes different from initial reservoir composition as pressure decline to values less than dew-point pressure. In-situ gas and condensate composition in the reservoir are changing accordingly. This paper develops a novel approach to obtain initial gas condensate reservoir composition from gas and liquid compositions taken from separator tests during several depletion stages. Based on the composition of mixed sample and initial reservoir composition, a set of novel correlations is developed for estimating initial gas condensate reservoir composition. The generalized reduced gradient (GRG) algorithm of iteration was used to tune the constant and exponents of the correlation based on available field data. The convergence criteria were to minimize the value of the squared sum, SS, of the difference between the real data and the estimated one

Two-phase flow choke performance in high rate gas condensate wells

Document ID: 145576-MSAbstract Multiphase flow occurs in almost all producing oil and gas/condensate wells. Wellhead chokes are special equipment that widely used in the petroleum industry to control flow rate, to maintain well allowable, to protect surface equipments, to prevent water and gas coning and to provide the necessary backpressure to reservoir to avoid formation damage from excessive drawdown. Accurate modeling of choke performance and selection of optimum choke size is vitally important for a petroleum engineer in production from reservoirs due to high sensitivity of oil and gas production to choke size. Two main approaches have been proposed for prediction of multiphase flow through chokes can be classified as either analytical or empirical and majority of correlations were developed for critical flow conditions. Although most of the correlations available to petroleum engineers are for critical flow but in lots of high rate gas/condensate wells subcritical flow occurs in large choke sizes.There is no empirical correlation for wellhead choke performance under subcritical condition for high rate gas condensate wells, especially in large choke sizes. The first aim of this paper is to develop a new simple empirical Gilbert type correlation for high rate gas condensate wells under subcritical flow in large choke sizes (40/64 in. to 192/64 in.) using non-linear regression analysis based on 61 field data points of 15 wells from ten different fields. The second is to extend the work of Al-Attar for high rate gas condensate wells flowing through large choke size under subcritical flow conditions and check the applicability and advantages.Finally, statistical comparison between these two approaches is done with different error parameters.Hamid Reza Nasriani and Azim Kalantarias

Gas Injection for Enhancement of Condensate Recovery in a Gas Condensate Reservoir

Gas condensate reservoirs suffer losses in well productivity due to near wellbore condensate dropout when the flowing bottom-hole pressure declines below the dew point pressure. Pressure maintenance and gas cycling are the common practices used in the oil and gas field to alleviate this problem and develop gas condensate reservoirs. The injection of dry gas into a retrograde gas condensate reservoir helps in vaporizing the condensate and increases its dew point. This article investigates the situation of one of the reservoirs located in southern Iran in Zagros area. First, based on the reservoir composition, the phase diagram has been plotted. Peng-Robinson equation of state for the equilibrium calculations and Lee-Kesler characterization of heavy fractions are used in this software. After that the effect of nitrogen, pure methane, a composition of ethane and methane, and carbon dioxide injections on reservoir recovery has been investigated and compared to a natural depletion scheme. The full system, including two separators and a stock tank, are simulated simultaneously and the effect of each type of injection on the liquid and gas production is investigated. Full mixing has been assumed in all of the injections studied. By comparing between the results it is concluded that in an injection process, required injection rate to maintain reservoir pressure above dew point pressure and avoid liquid formation in the reservoir for pure methane, a composition of ethane and methane, pure nitrogen and carbon dioxide, and liquid recovery in all cases are investigated. According to the results, with increasing ethane mole percent in the injecting gas a lower injecting rate for the same liquid recovery is needed. Because with increasing heavy components mole percent in injecting gas, average molecular weight of injecting gas, and reservoir gas becomes closer and there will be a better mixing between them and, therefore, liquid recovery will be improved. Thus, a composition of ethane and methane with more ethane mole percent is better than others. © 2015 Taylor and Francis Group, LLC

Resiliens i urban hydrologi : En studie av dagvattenhantering i Stockholms Stad

The environmental issues of storm water in the urban environment is addressed in political policies on many different governance levels. The concept of “sustainable storm water” in Europe uses the natural water cycle as a template for urban drainage, and the EU has a water framework directive (WFD) with a systems approach, using drainage basins as the starting point of all actions. In Stockholm, a new storm water strategy was adopted in 2015 with a sustainability approach, using much of the terminology from the WFD and the Swedish Water & Wastewater Association. To find new aspects related to sustainable development of storm water management in Stockholm, this study used a resilience framework of seven principles to analyse the implementation of the Stockholm storm water strategy (SSWS). A mixed method approach was used for a qualitative study, using interviews and a review of policy documentation as the main data sources, complemented by a desk study of literature on the subject of storm water management, as well as participation in some relevant workshops. To broaden the study, examples from a developing area within the Stockholm municipality, Stora Sköndal, was used, as well as another municipality in the Baltic Sea region; Helsinki (Finland). The SSWS leans on the legislation of the environmental quality standards (EQS) but is lacking in authority coordination on a national and municipal level in Stockholm. Diversity in problem formulations and solutions for infrastructure is high, so is the diversity of involved stakeholders, which is an indication of resilience. This in combination with the structure and communicational links having questionable functionality, leads to a complex and inefficient structure in management of storm water, which undermines the resilience of the system. However, since the SSWS and other connected policies (such as local programmes of measures and sustainability requirements) are new, the system is undergoing change, which shows some level of adaptability and complex adaptive systems (CAS) thinking, another resilience indicator. The implementation of the WFD on a municipal level is also connected to CAS thinking, as well as a polycentric governance system -one of the seven resilience principles of the framework used. Some of the main issues found within this study for building resilience in the SES are related to follow-up and responsibility division.Miljöfrågor inom dagvatten hanteras i policyarbete på flera olika institutionella nivåer. Begreppet ”hållbart dagvatten” utgår i Europa från den naturliga vattencykeln och EU:s vattendirektiv (WFD) har en systeminriktning som utgår från avrinningsområden istället för andra geografiska gränsdragningar. Stockholms Stad antog en ny dagvattenstrategi 2015 med en hållbarhetsinriktning, som innehåller mycket terminologi från WFD och publikationer från branchorganisationen Svenskt Vatten AB. För att hitta nya aspekter för en hållbar utveckling av dagvattenhantering i Stockholm använder denna studie ett teoretiskt ramverk inom resiliens,, som bygger på sju principer, i en analys av stadens dagvattensstrategi (SSWS). Blandade metoder användes för att genomföra en kvalitativ studie, där policydokument granskades tillsammans med intervjuer av nyckelpersoner, vilket kompletterades med en skrivbordsstudie av litteratur om dagvattenhantering samt deltagande i relevanta workshops. För att bredda studien användes exempel från ett planprogramsområde inom Stockholms kommun, Stora Sköndal, liksom en annan kommun i Östersjöområdet; Helsingfors (Finland). SSWS bygger juridiskt på miljökvalitetsnormerna, men brister i myndighetssamordning på nationell och kommunal nivå i Stockholm. Problemformuleringar och infrastrukturlösningar har hög mångfald, precis som involverade aktörer, vilket är en indikation på att systemet bygger upp resiliens. Detta i kombination med att struktur och kommunikationslänkar är något bristfälliga leder till en komplex och ineffektiv dagvattenhantering, vilket underminerar resiliensen i systemet. Eftersom SSWS och andra relaterade styrdokument (t.ex. lokala åtgärdsprogram och hållbarhetskrav) är nya, genomgår systemet förändringar, vilket visar på anpassningsförmåga och komplext, adaptivt systemtänk (CAS), vilket är en ytterligare resiliensindikator. Implementeringen av WFD på kommunal nivå är också kopplad till CAS-tänkande, liksom ett polycentriskt styrsystem - en av de sju principerna för resiliens i det teoretiska ramverket som används. Några av de huvudsakliga problem för att bygga resiliens som hittades i denna studie är relaterade till uppföljning och ansvarsfördelning

Evaluation of in-situ compositions in retrograde gas condensate fields

Production from gas condensate fields cause low condensate recoveries at surface facilities because of in-situ retrograde condensation and condensate build-up in the reservoir particularly in the vicinity of the wellbore. During depletion, the total composition of in-situ fluid (gas and condensate composition) changes from initial reservoir composition as pressure decreases to values less than Saturation (dew-point) pressure. This paper extends the line of the study conducted by our team (Nasriani et al., 2016) to attain initial in-situ composition from gas and liquid compositions taken from separator during several depletion stages. In our previous work, based on the composition of the mixed sample and initial reservoir composition, a set of novel correlations was developed for estimating initial gas condensate reservoir composition. But as carbon number increased, the predicted compositions by correlation became less accurate. In this study, in order to improve the prediction of in-situ compositions, the components with similar carbon numbers were grouped into a category. The generalised reduced gradient (GRG) algorithm of iteration was used to tune the constant and exponents of the correlation based on available field data