Advanced Control of Coiled Tubing Downhole Tools Addresses ExtremePermeability Contrast of Carbonate Water Injectors and Leads toUnprecedented Reservoir Sweep Efficiency

摘要

Efficient reservoir sweep is critical for operators to boost oil production in the Middle East.This taskbecomes particularly challenging in carbonate formations,which typically feature permeability rangingfrom microscopic pores to large cavernous vugs.Extreme heterogeneity disserves water injectors,leadingto nonuniform injection profiles.Consequently,water sweeping is inefficient and leaves significant residualoil behind.In the Mesopotamian Basin,the matrix stimulation approach was rethought to address highpermeability contrasts and produce the bypassed oil.The methodology relied on coiled tubing(CT)equipped with fiber optics and real-time downholemeasurements,a CT-deployed inflatable packer,and a high-pressure rotary jetting tool.The array ofdownhole readings was leveraged to ensure optimal use of the bottomhole assembly.The high-pressurerotary jetting tool was used in the first run to condition the wellbore tubulars across the inflatable packerplanned anchoring depth.In the second run,the inflatable packer was set at the target depth,and thestimulation treatment was selectively pumped either above or below the packer,depending on the depthof the interval of interest.The proposed stimulation technique was implemented in more than 40 wells,which included verticaland deviated water injectors,completed with 3 1/2-in.or 4 1/2-in.tubing and up to 7-in.casing,with twoto five perforated intervals averaging 30 to 50 m in total,temperatures ranging from 90 to 140°F,and anaverage meadured depth of 2500 m.The CT-deployed inflatable packer had an expansion ratio of up to 3 to1.CT real-time downhole measurements,such as CT internal pressure,CT annulus pressure,temperature,downhole axial forces,gamma ray,and casing collar locator(CCL),were instrumental to eliminate theuncertainties associated with changing downhole conditions and depth correlation.They also enabled acontrolled actuation of the downhole tools in subhydrostatic wells,as the pressure imbalance caused by thelow bottomhole pressure can generate loss of fluid flow and pressure across the tools.For the first time,theoperator was able to stimulate the tight rock in water injector wells,enhancing injection sweeping efficiencyand boosting oil production from offset wells.As a result of this campaign,production gains are estimated at 60,000 BOPD,and injectivity increased in average 2 times per intervention.This approach has now becomethe state of the practice for the operator to stimulate wells with high permeability contrast.This enhanced matrix stimulation technique,leveraged by CT and real-time downhole measurements,brings a new level of confidence to accurately and effectively deploy inflatable packers in wells withchallenging expansion ratio and low reservoir pressure.In addition,the proposed technique enablesstimulating tight rock across intervals with extreme heterogeneity,resulting in a more efficient sweep andan increase in oil production.