Michael Konopczynski, WellDynamics International Limited

WHILE THE UPSTREAM petroleumindustry struggles with maturing assets,dwindling reserves, and more difficultexploration environments, it seekslower development costs and speedyand maximum hydrocarbon reserverecovery. Intelligent well technology canimprove project performance for com-plex, challenging field developments.

A P P L I C A T I O N S

An intelligent well allows control of flowinto or out of the reservoir without phys-ical intervention, with or without down-hole sensors and monitoring. Since thefirst SCRAMS® system was installedseven years ago, over 185 intelligentwell systems have been installed world-wide by a number of suppliers and serv-ice companies.

The principal application ofintelligent well technology is theability to actively manage thereservoir recovery process.Intelligent wells can control thedistribution of water or gasinjection in a well between lay-ers, compartments or reser-voirs. They can restrict orexclude production of unwantedeffluents from different zones ina production well. The operatorcan manage where he injectswater or extracts oil to mobilizeunswept reserves. This is par-ticularly important for wellswith complex architecture,extended reach, long horizontalor multilateral wells, and forreservoirs characterized byhigh degrees of anisotropy, het-erogeneity or compartmental-ization.

Many reserve accumulations have beendiscovered that are too small to be eco-nomically developed on their own, andmany of these small reserves arestacked or in close proximity. Sequentialexploitation does not produce the oilfast enough or in great enough volumesto be economic under conventionaldevelopment methods. The solution is tocommingle the uneconomic reserves.Intelligent well technology addressesthe reservoir management and regulato-

ry concerns with commingling by pro-viding individual reservoir control, theability to prevent cross flow, and theability to allocate flow to each reservoir.

B U S I N E S S D R I V E R S

Increased hydrocarbon reserve recov-ery and accelerated production havelong been recognized as the key valuedrivers for adoption of intelligent welltechnology. However, the majority ofintelligent well applications to date havebeen in offshore platform and subseainstallations, driven largely by the eco-nomics of avoiding future well interven-tion costs.

Intelligent well business drivers will dif-fer for each application, and justifyingthe additional expense of intelligentwells based on increased reserve recov-ery can be difficult. In today’s financialenvironment, reduction in capital

expenditure of a development project iscritical. In terms of intelligent wells, thismeans that the same or better asset per-formance must be realized by fewerintelligent wells than the base casedevelopment plan with conventionalwells. Using extended reach horizon-tals, multilaterals or commingled com-pletions leveraged with intelligent welltechnology can reduce the number ofwells required to develop a structure. Toovercome the reservoir management

disadvantages of these complex wellarchitectures, intelligent well technolo-gy provides monitoring and control ofthe movement of fluids downhole.

Finally, downhole sensing allows theoperator to better understand the reser-voir and recovery process and to makefaster and more informed operationaldecisions. The dividends are improvedutilization of asset infrastructure,reduced effluent production, accelerat-ed production, improved hydrocarbonrecovery, and better selection of infillwell locations and numbers of wells toefficiently develop an asset.

I N T E L L I G E N T C O M P L E T I O N S

The main functionalities of intelligentwells are downhole flow control andsensing. There are three key compo-nents used in most intelligent well com-pletions: downhole flow control valves

or interval control valves (ICVs);downhole sensors; and isolationpackers. Ancillary componentsand systems, including powerand communication lines,clamps, splice subs, surface andsub-surface control systems,and data acquisition and controlsystems, support these compo-nents.

Several flow control capabili-ties, actuation methods andchoke trim designs are avail-able. Downhole flow controlvalves may be binary (on-off),limited discrete positioning, orinfinitely variable. Actuationmethods may be hydraulic (bal-anced or mechanical/gas springreturn), electric, or hybrid elec-tro-hydraulic. The selection ofthe right flow control option iscritical, as it may have an

impact on the number of zones/intervalsthat can be realistically controlled inone well, and may affect the overall reli-ability of the integrated system.

There are many sensor technologyoptions. The most widespread downholesensor technology in use is the electron-ic pressure/temperature gauge. Combin-ing pressure/temperature gauges with adifferential pressure flow measurementelement, such as a venturi, allows sup-pliers to offer downhole flow meters.

March/April 2004 D R I L L I N G C O N T R A C T O R 37

Intelligent wells can improve reservoir performance

In the Saih Rawl Multi-Lateral Waterflood in Oman, lateral wells of fourto seven legs are typically drilled for both producers and injectors withproducers overlaying injectors.

38 D R I L L I N G C O N T R A C T O R March/April 2004

Optical fiber distributed temperaturesensors, pressure sensors, and passiveacoustic flow meters are now maturetechnologies.

To independently control separate inter-vals, zones or laterals of the wellbore,isolation packers are required, andthese must provide for feeding powerand communication lines through theisolating elements. Surface data acqui-sition and control systems are neces-sary to complete the interface betweenthe operator and the downholeSmartWell tools.

D I G I T A L H Y D R A U L I C S

The Digital Hydraulics system is aclosed loop, all hydraulic actuator con-trol system. It uses digital (binary) codeimpressed on the hydraulic lines to com-mand a suite of downhole flow controlvalves or ICVs. The patented DigitalHydraulics concept uses the logicalpresence of pressure or absence of pres-sure to communicate between the sur-face controller and the downhole tools.The precise pressure level or time for

which it is applied is unimportant. Thissystem is simple to operate yet givesreliable command and communicationto a large number of tools while mini-mizing the number of control lines.

The key component of the DigitalHydraulics system is the DigitalHydraulics “decoder“ unit, a device thatdetects and responds to the sequencedapplication of control line pressure toenable communication with the ICVactuator piston. All decoder units in thewell are connected to all the hydrauliccontrol lines so that they will respond toonly one sequence of applied pressures.Once activated, the decoder unit allowsU-tube communication between two ofthe downhole control lines across theICV piston. With this technology, threecontrol lines can control up to six down-hole tools, and four control lines cancontrol up to twelve downhole tools.

Seven Digital Hydraulics systems havebeen installed. The greatest number ofzones controlled in one well with theDigital Hydraulics system is five zones,

which is also the record for the greatestnumber of zones controlled in an intelli-gent well.

D I G I T A L H Y D R A U L I C S I N O M A N

The Saih Rawl Shuaiba reservoir in cen-tral Oman is a low permeability lime-stone reservoir producing light oil withpressure maintenance by means of awater flood. Extensive developmentstarted in the early 1990’s when multi-lateral horizontal well technologyenabled economic production rates fromwells and sustainable water injection forthe water flood. Multilateral wells offour to seven legs are typically drilledfor both producers and injectors withproducers overlaying injectors.

To improve water flood efficiency andreduce water cut of produced fluids,Petroleum Development Oman installeda Digital Hydraulics SmartWell in a SaihRawl well that allows each of the fourlaterals legs to be independently openedand closed at will from surface usingthree hydraulic lines. The intelligentwell system has been integrated withthe electric submersible pump installa-tion by providing a hydraulic discon-nect, allowing replacement of the elec-tric submersible pump in the upper com-pletion section without affecting thelower intelligent well section.

The intelligent completion was installedin the Saih Rawl well in July 2002 andproduced shortly thereafter. Severalproduction tests were conducted byopening and closing each of the four lat-erals individually and in combination, toestablish the maximum oil productionpotential and optimum completion con-figuration for maximum oil and mini-mum water production. The SmartWellcompletion immediately raised produc-tion. Initial results indicated a reductionin water production by 28% while net oilproduction increased by 1,437 b/d. Thewell performed beyond expectationswith an incremental 1,200 b/d sixmonths after the installation. All DigitalHydraulics systems operated flawlessly.

R E F E R E N C E

The case history in this article is basedupon OTC paper 15134, The Use of Sur-face Controlled Hydraulic IntervalControl Valves for the Management ofWater Production in the Saih Rawlfield, Sultanate of Oman, by M Boyle,J Earl, and S Al-Khadori. n