Kuliah-13Kuliah 13Peretakan Hidrolik (lanjutan)

Komplesi & Kerja Ulang Sumur(2 SKS)

Dosen : Ir Andry Halim MMDosen : Ir. Andry Halim, MMUniversitas Trisakti

2012

Objective/SasaranObjective/Sasaran

Memahami konsep-konsep PeretakanMemahami konsep konsep PeretakanHidrolik

Memahami teknik perencanaan Peretakan Memahami teknik perencanaan PeretakanHidrolikM h i di d i Memahami penerapannya di duniaPerminyakan

Daftar Pustaka

Allen S.O. and Robert A.P. Production Operation, Vol. I Oil and Gas Cons ltant International IncGas Consultant International Inc.

Schlumberger Hydraulic Fracturing. Peter E. Clark,Well Completions : Stimulation and Work Over. Unocal Completion training/Course Schlumberger Hydraulic Fracturing Training Material Pertamina Hulu Teknik Produksi Jakarta 2003 Pertamina Hulu, Teknik Produksi , Jakarta, 2003 H.K. Van Poolen,Well Completion and Stimulations Program. Peter E. Clark,Well Completions : Stimulation and Work Over. Jonathan Billary Well Completions Design PetroleumElsevier Jonathan Billary, Well Completions Design , PetroleumElsevier,

2009 Semua buku perihal Komplesi dan uji Sumur Semua Jurnal tentang Komplesi dan uji SumurSe ua Ju a te ta g o p es da uj Su u

FORMATION FRACTURING

OBJECTIVES

The objective of hydraulic fracturing for well stimulation is to increase well productivity by creating a highly conductive path (compare to reservoir permeability) some distance away from wellbore into the p y) yformation.

Fracture InitiationA hydraulic fracture treatment is accomplished by pumping a suitableA hydraulic fracture treatment is accomplished by pumping a suitable fluid into the formation at a rate faster than the fluid can leak off into the rock. Fluid pressure is built up sufficient to overcome the earth compressive stress holding the rock material together. The rock then parts or fractures along a plane perpendicular to the minimum compressive stress in the formation matrix.

Fracture ExtensionAs injection of frac fluid continues, the fracture tends to grow in width

fl id i th f t t d th f t f kas fluid pressure in the fracture, exerted on the fracture face, works against the elasticity of the rock material. After sufficient frac fluid pad has been injected to open the fracture wide enough to accept proppant, sand is added to the frac fluid and is carried into the p pp ,fracture to hold it open after the job.

The growth upward or downward may be stopped by a barrier formation; downward growth may also be stopped by fallout of sand ; g y pp yto the bottom of the fracture. The growth outward away from the wellbore will be stopped when the rate of frac fluid leakoff through the face of the fracture into the formation equals the rate of fluid injection into the fracture at the wellboreinto the fracture at the wellbore.

Mechanics of Fracturing

S

vRegional Rock Stresses

h2v = Total vertical stress, psih1

Total vertical stress, psi= 0.007 D= average rock density, lb/ft= depth, ft

D

= 0.007 D Pr= formation pore pressure, psi

Prv

h1 = Maximum principal horizontal matrix stressh2 = Maximum principal horizontal matrix stress

= (v Pr) 1 - h= Poissons ratioHorizontal Matrix stress depend on rock properties and pore pressure.

Horizontal FractureAssuming vertical components of force are exerted against the formation, the condition necessary for horizontal fracture initiation isformation, the condition necessary for horizontal fracture initiation is that the wellbore pressure must exceed the vertical stress plus vertical tensile strength of the rock plus pore pressure.

V ti l F tVertical FractureCondition for vertical fracture initiation depend on the relative strength of the two principal horizontal compressive stresses.

Fracture Propagation

Fracture OrientationThe fracture will propagate in a plane perpendicular to the minimum effective matrix stress. Usually the minimum stress is horizontal, and a vertical fracture results.Where horizontal matrix stress are unequal, there will be a preferred direction for the vertical fracture.

Fracture Closure PressureTo hold the fracture open after initiation (or to just keep it from closing), the pressure in the fracture must exceed the pressure by an amount equal to the minimum effective rock matrix stress. This pressure is usually called the fracture closure pressure. The fracture gradient is the fracture closure pressure divided by depth.

Fracture Propagation PressureAs the fracture is extended the pressure in the fracture at the wellboreAs the fracture is extended, the pressure in the fracture at the wellbore (fracture propagation pressure) increases as a result of fluid friction required to push the frac fluid through an increasing distance toward the tip of the fracture. Other factor that can increase fracture propagation pressure is the increasing of pore pressure in the rock near the fracture due to fluid leakoff (also increased closure pressure).

Net Fracture PressurePressure in the fracture in excess of the fracture closure pressure is the net fracture pressure. Net fracture pressure acts against the elasticity, or Youngs modulus, of the rock to open the fracture wider. During the fracture job, the net fracture pressure (Nolte Plot) can be used as an indicator of fracture extension (see next plot).

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I - Confined height; unrestricted extensionII - Unstable growth, or fluid lossIII - Growth restriction

II III

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p

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e IV - Unstable height

IV

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ILo

Log Time

Production Increase From Fracturing

Reasons for production increases from fracturing are :1. New Zones Exposed2. Reduced permeability bypassed (bypassed Damage)3. Flow pattern in reservoir changed from radial to linear

Propping the FractureThe objective of propping is to maintain desired fracture conductivityThe objective of propping is to maintain desired fracture conductivity economically. Fracture conductivity depends upon a number of interrelated factors :

Type, size, and uniformity of the proppant Degree of embedment, crushing, and or deformation of proppant Amount of proppant Manner of placement

Desirable Properties For Propping Agents Size and Uniformity Strength Physical Properties (Acid solubility, roundness, and density) Cost

Frac FluidsBasically oil or water fluids are used to create extend and placeBasically oil or water fluids are used to create, extend, and place proppant in the fracture.

Fluid Properties and ModificationFrac fluid consideration :

Fluid viscosity Fluid loss Friction loss (down the pipe) Friction loss (down the pipe) Proppant carrying ability High temperature stability Formation damage Fracture clean up Mixing and storage problems Cost

Frac Job Design

1 S l t th i ht ll1. Select the right wellConsider the risks involved condition that increase risks are :

Less than 15-20 ft of shale between the frac interval and gas or water sand.water sand.

Others things being equal fractures tends to move upward due to sand fallout to the bottom of the fracture sometimes this effect can be maximized.Water or gas contact nearb and located in a direction so that Water or gas contact nearby and located in a direction so that fracture would go toward it.

Well producing high GOR or WOR are poor candidates for fracturing unless it is free gas or water from a zone which can be g gshut off.

2. Design for the specific wellDesign parameter to be considered are :

Lithology and mineralogy of the formation Lithology and mineralogy of the formation Fracture geometry parameters (Young modulus, Poissons ratio,

formation boundary horizontal matrix stress) Reservoir fluids and reservoir pressure/energy Physical well configuration

3. Optimize design over several jobsUsually the experience gained in several carefully designed and

evaluated jobs is necessary to achieve optimum design.

4. Utilize calculation procedures as a guide4. Utilize calculation procedures as a guideTreatment design must specify the following parameters :

Frac fluid typeFluid volumeFl id i it d fl id l h d lFluid viscosity and fluid loss scheduleProppant size and typeProppant scheduleInjection rate schedulej

Basic design procedures :Determine required fracture length and conductivityDetermine frac fluid characteristic and injection ratesDetermine frac fluid characteristic and injection ratesDetermine a treatment pumping and proppant injection

scheduleComputerization speeds calculation procedures

Hydraulic Fracturing Equipment Fluid storage Fluid storage Proppant storage Blender Primary high pressure pumps The Operational control centre

Frac Job EvaluationTo evaluate the success of a frac treatment and help designTo evaluate the success of a frac treatment and help design succeeding treatments, it is necessary to know :

What sustained production increase was obtained What zone or zones were actually stimulated. For vertical fractures, what was the fracture height and azimuth. What was the fracture length What was the fracture conductivity

PERENCANAANPERENCANAAN PEREKAHAN HIDROLIK

PERENCANAAN PEREKAHAN HIDROLIK

PERENCANAAN PEREKAHAN HIDROLIK

PERENCANAAN PEREKAHAN HIDROLIK

PERENCANAAN PEREKAHAN HIDROLIK

CONTOH SOAL

CONTOH SOAL

CONTOH SOAL

CONTOH SOAL

CONTOH SOAL

CONTOH SOAL

CONTOH SOAL

CONTOH SOAL

CONTOH SOAL

QUESTIONS ?QUESTIONS ?

PR-13PR 131. Apa yang dimaksud dengan fracture initiation. Jelaskan secarap y g g

singkat2. Apa yang dimaksud dengan fracture extension. Jelaskan secara

singkat3. Jelaskan tahap2 fract job design4. Sebutkan hydraulic fracturing equipment