petsoc-97-11-p-diseÑo hidraulico en pozos horizontales en recuperacion termica

8/6/2019 PETSOC-97-11-P-DISEO HIDRAULICO EN POZOS HORIZONTALES EN RECUPERACION TERMICA

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HYDRAULIC DESIGN OF THERMAL HORIZONTAL WELLS

M.MCCORMACK

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THE PETROLEUM SOCIETY PAPER 97-11 Hydraulic Design of Thermal Horizontal Wells, M. McCormack Fractical Solutions Inc., ELAN Energy Inc.

This paper is to be presented at the 48th Annual Technical Meeting of The Petroleum Society in Calgary, Alberta, Canada, June 8 - 1 1, 1997. Discussion of this paper is invited and may be presented at the meeting if filed in writing with the technical program chairman prior to the conclusion of the meeting. This paper and any discussion filed will be considered for publication in CIM journals. Publication rights are reserved. This is a pre-print and is subject to correction. ABSTRACT

well and single well SAGD process shows that insulated tubing may be beneficial under various scenarios while Many recent projects have demonstrated that the injection of it may be unnecessary for others. steam into horizontal wells can recover significant quantities of heavy oil at economic rates. A variety of 2. Guidelines for the distribution of steam between tubreservoirlwellbore processes have been utilized, including and annulus in horizontal injectors. dual well SAGD, single well SAGD, cyclic steam stimulation and steam drive, as well as many hybrids 3. The basic design considerations for the gas/steam lift Specific installations may also include the use of vertical thermal production wells. wells, particularly as injectors. The proper distribution of steam

injection and the INTRODUCTION management of inflow of hot produced fluids into horizontal wellbores is essential to the successful operation of these The use of horizontal wells for thermal recovery projects. As typical wells are 500-1000 m in length, there is increased significantly during the past decade. There a significant surface area for heat exchange to occur when now a wide range of installations including dual well steam there is fluid flow

in both the tubing and annulus. If assisted gravity drainage (SAGD), single well SAGD combined with inappropriate designs and operations there multi-laterals and various steam drive configurations. can be undesirable and unexpected effects on the overall performance Common to all these applications is the flow of mixtures

steam/water/oil over a considerable range of temperatures Specific examples discussed include: Due to the length of these wells, typically greater than 1. The performance of circulation systems for both dual


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THE PETROLEUM SOCIETY

Hydraulic Design ofThermal Horizontal Wells

M. McCormackFractical Solutions Inc., ELAN Energy Inc.

PAPER 97-11

This paper is to be presented at the 48th Annual Technical Meeting of The Petroleum Society in Calgary, Alberta, Canada, June 8 - 11,1997. Discussion of this paper is invited and may be presented at the meeting if filed in writing with the technical program chairman priorto the conclusion of the meeting.This paper and any discussion filed will be considered for pUblication in CIM journals. Publication rightsare reserved. This is a pre-print and is subject to correction.

ABSTRACT

Marcy recent projects have demonstrated thot the injection ofsteam into horizontal wells can recover significant quantitiesof heavy oil at economic rates. A variety ofreservoir/wellbore processes have been utilized, includingdual well SAGD, single well SAGD, cyclic steamstimulation and steam drive, as well as many /rybrids.Specific installations may also include the use of verticalwells, particularly as injectors.The proper distribution of steam injection and themanagement of inflow ofhot produced fluids into horizontalwellbores is essential to the successful operation of theseprojects. As typical wells are 500-1000 m in length, there isa significant surface area for heat exchange to occur whenthere is fluid flow in both the tubing and annulus. Ifcombined with inappropriate designs and operations therecan be undesirable and unexpected effects on the overallperformance.Specific examples discussed include:1. The performance of circulation systems for both dual

well and single well SAGD process shows thot insulatedtubing may be beneficial under various scenarios whileitmay be unnecessary for others.

2. Guidelines for the distribution of steam between tubingand annulus in horizontal injectors.3. The basic design considerations for the gas/steam lift ofthermal production wells.

INTRODUCTIONThe use of horizontal wells for thermal recovery hasincreased significantly during the past decade. There arenow a wide range of installations including dual well steamassisted gravity drainage (SAGO), single well SAGO,multi-laterals and various steam drive configurations.Common to all these applications is the flow of mixtures ofsteam/water/oil over a considerable range of temperatures.Due to the length of these wells, typically greater than


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1200 m measured depth, and the relatively high flow rates,100+ m3/d , there is a potential of encountering significantpressure drops and/or high rates of heat exchange. Adverseeffects can include:

Uneven distribution of injected and produced fluids.Significant variations in temperature along the well.Unstable behaviour in steam/gas lift systems.

Since one of the major advantages of a thermal horizontalwell is the capability to . contact a larger volume ofreservoir, it is important that the issues of steam injectionand production distribution be evaluated by numericalmodelling during the design phase, prior to fieldinstallation. In addition, numerical modelling of thewellbore can assist in evaluating field performance, this isparticularly applicable to situations where temperature dataalong the length of the well is unavailable. Carefulapplication of numerical wellbore simulation can also leadto insights into the actual reservoir processes, and can assistin constraining numericalreservoir simulators.Originally, thermal wellbore simulation was limited to afew analytical techniques. Over the past several decadesthese have evolved to comprehensive numerical models thatcan model increasingly complex situations. In the future thetrend will be to increasing integration with reservoirsimulation.

NUMERICAL SIMULATION TECHNIQUESThe principle components of a successful numericalsimulation of thermal horizontal wells include:

Heat transfer coefficients across films and insulation.Conduction heat transfer into the frmation.Viscosities, enthalpies and interfacial tension data formixtures of steam/water/oll/gas.Two-phase flow correlations to predict frictionalpressure losses and flowing densities.Capabilities to model a variety of wellboreconfigurations, ~ c l u d i n g circulating systems. -Ability to transmit.fluiqs to and from the reserVoir.

In many situations the solution can be simplified byaccepting that certain parameters' or phenomena areinsignificant towards the .final solution. For example, duringthe first few days of injection into a cold injection well, it isunnecessary from the wellbore hYdraulic perspective toadjust the formation conduction heat losses to account for2

the enthalpy of the injected fluid. At the other extreme it ialso beneficial to assume that there are essentially noconduction heat losses to the region of a reservoir which habeen on injection for a substantial period of time.The QFLOW thermal wellbore simulator was used to obtaithe calculated results for this study. This model consists of a100 unit finite element grid capable of handling severaflowing streams. Two-phase fluid flow pressure drop andflowing density calculations are accomplished through theBeggs & Brill correlations, modified to control severadiscontinuities. The gaslliquid compositions are handled byan equation of state. Heat transfer coefficients arecalculated from general industry correlations. It should benoted that there are essentially no formal laboratory studiesevaluating the integration of all of these correlations undethe conditions present in thermal horizontal wells.However, experience with modelling actual fieldinstallations has identified no major deficiencies to-date.Configurations with multiple flow streams can result insituations with highly non-linear behaviour, creating asignificant potential for problems with numericaconvergence. The simulator handles such situations bygradually increasing the heat exchange interaction betweenthe various flowing streams. This allows the solution togradually explore the non-linear regions, greatly reducingconvergence sensitivities.In many situations it is necessary to allow for injection to orproduction from the reservoir. This can significantly changethe flowrate, composition and temperature of the system. Asimplified approach is to allow for a .constaninflow/outflow along a specified region of the well. More~ o m p l i c a t e d methods include varying degrees of coupling toreservoir simulators.

CIRCULATING SYSTEMS DUALWELL SAGOIn a dual well SAGD it is a common requirement to start-upthe wells with a steam circulating procedure, heating thereservoir between the wells via conduction heating. Foroptimum results it is desired to place steam along the entirelength of the annulus at the minimum possible injectionrate.In the simplest arrangement the steam is injected down thetubing and the return flow is up the annulus. If bare tubingis used in the vertical/slant section of the well it is difficultto deliver steam to the end of the well. Calculated results ofa typical installation are provided in figure 1; as per the


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petsoc-97-11-p-diseÑo hidraulico en pozos horizontales en recuperacion termica

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