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1、Advances in the Technology of Formation Damage Control,Significance of Carrying out the Technology,Discover target formations without delay in the exploration stage Related to enhancement of the production rate of oil wells and the economic benefit of exploitation Be beneficial to increasing ultimat
2、e recovery and stable production,Aspects Involved in the Technology of Formation Damage Control,Core Analysis Evaluation of Formation Sensitivity and Damage Induced by Working Fluids Study and Diagnosis of Formation Damage Mechanisms Formation Damage Control During Drilling Formation Damage Control
3、During Completion Formation Damage Control During production Field Evaluation of Formation Damage Evaluation & Analysis of Overall Effectiveness for Formation Damage Control,1. Formation Damage & Reservoir Productivity,The Ideal Reservoir Model,Schematic of skin pressure differential,Correlation bet
4、ween skin pressure differential & skin factor,where，h thickness of target formation，m； P skin pressure differential，MPa； q production rate，m3/d； o viscosity of crude oil，mPas； Bo volume factor，dimensionless; S skin factor, dimensionless.,Skin factor a measure of damage,The skin factor, S, is related
5、 to permeability and depth of invasion as follows: where: Kd = altered zone permeability K = unaltered formation permeability rd = radius of altered zone rw = radius of wellbore For: S 0 formation is probably damaged since Kd K,The CNPC Regulation for evaluation of formation damage for homogeneous s
6、andstone formations (CNPC 关于均质砂岩油气层损害的评价标准),Extent of damage: slight intermediate serious S 0 2 2 10 10,Formation damage accelerates decline of production rate,Formation Damage Results in Delayed Payout,Impact of Formation Damage on Production Rate,S,Economic Implications of Formation Damage,FD$L =
7、365 qo * P * DR P oil price, FD$/bbl qo undamaged production rate, STB/D DR damage ratio,Annual Revenue Loss Per Oil Well,The impact of formation damage on reservoir productivity can be evaluated by computing the annual revenue loss per well (FD$L) at a given oil price, P, as described by the equati
8、on below.,Formation Damage Can Result in Excessive Loss of Revenue,Correlation Between Flow Efficiency & Skin Factor,Ef = Jactual /Jideal = 7/(7 + s) when s = 1.75时， Ef decrease by 20% when s = 7.0时， Ef decrease by 50% （After Luo Yingjun, Petroleum Industry Press, 1996）,Origin of the Equation,Undama
9、ged production rate： Actual production rate： For a given producing drop, Assume ln(re/rw) 7，,Effect of formation damage on productivity,2. Types & Mechanisms of Formation Damage,2. Mechanisms of Formation Damage,Mud solids plugging （泥浆固相堵塞） Fines migration （微粒运移） Clay swelling （粘土水化膨胀） Emulsion/wate
10、r block（乳状液堵塞 / 水锁） Wettability alteration （润湿性改变） Reduced relative permeability （相对渗透率下降） Organic scale (asphaltene/paraffin) precipitation 有机垢（沥青质 / 石蜡）沉积 ,2. Mechanisms of Formation Damage,Inorganic scale precipitation（无机垢沉积） Injected particulate plugging（注入水微粒堵塞） Secondary mineral precipitation（
11、二次矿物沉淀） Mineral transformation（矿物转换） Bacteria plugging（细菌堵塞） Sanding（出砂）,Formation Damage Severity Scale for Various Stages of Well Development & Reservoir Exploitation,Inorganic Scaling Problems,Inorganic scaling (CaCO3, CaSO42H2O, SrSO4, BaSO4) Induced by cementing and completion fluid filtrates r
12、ich in Ca2+ and Ba2+ Induced by fluid-fluid incompatibility from drilling, completion, workover and water injection operations Induced by ion exchange,Organic Scaling Problems,Organic Scales (paraffins & asphaltenes) organic scales occur due to changes in crude oil composition, temperature and press
13、ure. As gas saturated oil is produced into the wellbore, pressure drops across the perforation, the crude temperature therefore drops (Joule-Thompson effect). The drop in temperature then shifts the thermodynamic equilibrium between the paraffins, asphaltenes and resins in the crude oil to induce or
14、ganic precipitation.,Organic Scaling Problems,The drop out of organic scales is dependent on the temperature differential between the bulk crude stream and the pipeline and also on the Reynolds number. The larger the temperature differential, the greater the chances of paraffin deposition.,Water blo
15、ck Dp = 2s (1/R1 1/R2),Oil/water Interfacial tension vs. Concentration of ABSN,Effect of Surfactants & Swi on Damage Ratio for Sandstone cores,Wettability,so = sw + ow cos where： so = IFT for solid/oil phase sw = IFT for solid/water phase ow = IFT for water/oil phase = contact angle,USBM tests Amott
16、 tests Contact angle measurements,Wettability Alteration of Reservoir rocks induced by Drilling Muds,Effect of wettability alteration on relative permeability to oil & water,(After Thomas, D.C., Hsing, H. and Menzie, D.E.,1996),Effect of Wettability on Waterflood Performance,o = 1.74 cp, w = 0.35 cp Taken from Owens and Archer,Components of Oil-Based Muds Used to evaluate Wettability Alteration (After Yan, 1993),From Ba
