SPE Distinguished Lecturer Program

Transcription

1 SPE Distinguished Lecturer Program Primary funding is provided by The SPE Foundation through member donations and a contribution from Offshore Europe The Society is grateful to those companies that allow their professionals to serve as lecturers Additional support provided by AIME Society of Petroleum Engineers Distinguished Lecturer Program 1

2 Hydraulic Fracturing Materials: Application Trends & Considerations Harold D. Brannon BJ Services Company Society of Petroleum Engineers Distinguished Lecturer Program 2

3 Outline Hydraulic Fracturing Fracturing Material Functions Fracturing Fluids & Additives Recent trends Emerging Technologies Proppants Recent trends Emerging Technologies Summary 3

4 What is hydraulic fracturing? A process of placing proppant into fractures created in oil and gas zones to increase the flow of oil or natural gas to the wellbore. Fractures are created by pumping fluids at high pressures and rates. Proppant is added to the fluid, which when pumping has ceased, props the fractures to keep them open. The propped fractures provide highly conductive flow paths for the hydrocarbons to reach the wellbore

5 Hydraulic Fracturing World-wide application ~ 100,000 wells annually 90% of gas wells 70% of oil wells Predominantly used for low-permeability reservoirs High permeability applications increasing Complex operation Requires knowledge and high competence in a number of areas of engineering and science

6 Fracturing Fluids Functions: Transmit hydraulic pressure to fracture Transport proppant into the fracture Desired Characteristics Non-hazardous, environmentally benign Compatible with reservoir Low wellbore friction pressure Control leak-off to the formation Transport & suspend proppant until closure Non-damaging to fracture conductivity 6

7 Fracturing Systems & Trends Aqueous Slickwater Linear polymer-viscosified fluids Crosslinked polymer gels Viscoelastic surfactant gels Non-aqueous Gelled oil Nitrogen gas Emulsions Gelled methanol Non-Aqueous Fluids VES Slick Water Crosslinked Gels Linear Gels % of worldwide fracturing treatments BJ Services Company,

8 Aqueous Systems % of US Fracturing treatments Slick Water Linear Gels 1998 Slick Water Crosslinked Gels 2009 Crosslinked Gels Linear Gels Strong transition to slickwater and low viscosity, non-crosslinked fluids driven by the increased development of ultra-low permeability reservoirs (from 21% to >50% of N. American treatments) 8

9 Slickwater Water with acrylamide polymers PAA polymers reduce pipe friction Minimal polymer loading with low system costs Low viscosity Poor fluid efficiency, proppant transport Minimal fracture damage potential 9

10 Complex Network Fracturing Slickwater is the preferred fluid for naturally fractured shale reservoirs (ultra low perm.) Massive volume of low viscosity fluids facilitates development of a large and complex fracture network Poor proppant transport and suspension capabilities typically necessitate high injection rates

11 Guar Polymer Systems Guar is the most commonly used gelling agent for viscosifying fracturing fluids -- Naturally occurring polymer extracted from guar seeds Cost effective, used widely in food stuffs and cosmetics May be processed to enhance fluid properties in harsh environments Improved guar products yield much lower insoluble residues and higher viscosity per unit Guar pods, seeds, splits, and powder Modern Fracturing (2007) 11

12 Crosslinked Polymer Systems Crosslinking a polymer exponentially increases the fluid viscosity 10 to 60 cp increased to 100 to > 1000 cp Crosslinking : Increases treating friction Improves fluid efficiency (leak-off control) Improves proppant transport Increases gel damage potential 12 Crosslinked Gel Vortex Closure, progression over 3 minutes, Modern Fracturing (2007)

13 Guar Polymer Systems Linear Guar pptg BHSTs to 200 o F ph 6-8 Borate-X-linked pptg Guar BHSTs to 300 o F ph 9 12 Low viscosity Shear stable Poor proppant transport Best retained conductivity High viscosity Shear stable Good proppant transport Good retained conductivity Zirconium-X-linked pptg CMHPG BHSTs to 375 o F ph 4-10 Moderate viscosity Shear sensitive Good proppant transport Fair retained conductivity Modern Fracturing (2007) 13

14 Gelled Aqueous Systems Linear Gels Linear Gels VES Crosslinked Gels Conv. X-linked Gels Low Loading X-linked Gels Linear gel usage increased, mostly due to unconventional reservoirs applications in lieu of slickwater Crosslinked, high viscosity guar systems using low polymer loadings replaced up to 65% of previous crosslinked guar system usage Viscoelastic surfactant gels (VES), usage increased to 4% 14 of non-slickwater, gelled aqueous fluids

15 Low Guar Crosslinked Fluids High viscosity yield per unit of polymer Provides for up to 50% polymer loading reduction Lower friction pressure Reduced loading results in less gel damage Higher regained conductivity Improved fluid recovery and cleanup Lower Flow Initiation Stress (FIS) 15

16 Viscoelastic Surfactant Fluids Viscoelastic surfactants used to gel fluids No polymers Operationally simple Components multi-functional No need for biocide, buffer, clay control, etc. Poor leakoff control Good transport Non-damaging Recovered fluids recyclable 16

17 Emerging Fluid Technologies High Density Fracturing Fluids Bottomhole treating pressures > 15,000 psi Crosslinked guar in high density brine Reduces surface treating pressure & 20,000 ft, 12.5 ppg brine provides for a 4,300 psi reduction in treating pressure 17

18 Emerging Fluid Technologies Ultra High Temperature Systems: BHSTs from 350 o F > 500 o F Synthetic polymer-based Stable > 2 hrs at 450 o F Provides for execution of job sized sufficiently for proper stimulation without the requirement of a cool-down pad 18

19 Emerging Fluid Technologies Ultra-high Quality Foams +/- 95 Quality foam (N 2, CO 2, or mixed gas) Favorable environmental impact characteristics Minimized impact on water supply Foamers chemically benign Most applicable for low-pressured reservoirs Additional gas volumes enhance recovery Non-damaging, 100% regained conductivity 19

20 Emerging Fluid Technologies Associative Thickener Systems Non-polymer gelled fluid Relies on ionic association of additives Attributes similar to VES systems Thickening initiated by elevated temperature, Viscosity begins to increase at 150 o F Rheologically stable to >250 o F Non-damaging 100% regained conductivity Environmentally benign

21 Emerging Fluid Technologies Environmentally Acceptable Chemistries Governmentally driven Most active in US & Europe Growing activities globally In US, applies to all frac appls Replacement characteristics Performance functionality Safe to handle Low toxicity Biodegradable Targeted Materials Diesel & BTEX Bacteriacides Clay control Surfactants Non-emulsifiers Corrosion inhibitors 21

22 Proppants Proper placement creates a conductive pathway from the reservoir to the wellbore Ottawa Frac Sand Proppant is the only material which is intended to remain in the reservoir after a hydraulic fracturing treatment completion and cleanup Brown Frac Sand 22 Low Density Ceramic

23 Proppant Characteristics Transportability particle density, size, shape fluid velocity, viscosity, density Particle in-situ stresses particle composition, size, shape Fracture conductivity particle concentration, size, packing 23

24 Proppant Usage Trends Tons 200, , , , , , , , , , ,000 90,000 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10, White Sand Brown Sand Resin/Ceramics/Speciality Total : 660% increase in proppant usage : Sand has increased from 70% to 85% of total Data courtesy of BJ Services Company USA

25 Proppant Size Usage Trends Tons 170, , , , , , , ,000 90,000 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10, White 20/40 White 12/20 White 16/30 White 30/50 White 40/70 & 30/70 White 20/50 White 100 Mesh Total : 20/40 reduced from >90% to <50% of total usage : 30/50, 40/70, & 70/140 usage increased > 1,000% Data courtesy of BJ Services Company USA

26 Proppant Conductivity Conductivity (C f = k f w) is a measure of the fracture s ability to transmit fluids C f D contrasts the transmissibility of the propped fracture to that of adjacent reservoir C FD k f kx w f k f = fracture permeability w = fracture width k = reservoir permeability X f = fracture length 26

27 Fracture Conductivity A key design parameter for successful stimulation Subject to change over the life of the well due to: Proppant particle failure Effective stress increase with production Damage: gel residuals, embedment, fines Non-Darcy or multiphase flow 27

28 Proppant Selection Most typically based upon propped fracture conductivity at reservoir closure pressure 28

29 Fracture Conductivity Higher proppant concentrations generally provide greater conductivities due to the increased imparted width. The exception is partial proppant monolayers Strong industry trend driven by increased unconventional resource development to use of smaller diameter proppants at low concentrations 29

30 Effect of Proppant Concentration Modern Fracturing (2007) 30

31 Effect of Proppant Size Modern Fracturing (2007) 31

32 Residual Fluid Damage Fracture conductivity damage from crosslinked gelled fracturing fluids with breakers typically ranges from 20-90% (Penny (Stim-Lab), 1992) 32

33 Gel Damage Regained Conductivity vs. Breaker Concentration No Breaker Low Breaker Moderate Breaker High Breaker % Regained Conductivity VES, 2% Slickwater B/HE Guar, 25 ppg Linear Guar, 40# Zr/CMG, 20 pptg B/Guar, 40 pptg Zr/CMHPG, 30 pptg Data courtesy of Stim-Lab Consortia 33

34 Emerging Proppant Technologies Reduced density proppants (ultra-lightweight) to improve proppant transport and placement for enhanced conductive fracture area Transport Distance, ft. Bauxite, 3.50, 40/70 Sand, 2.65, 40/70 LWC, 2.55, 40/70 Sand, 2.65, 70/140 ULWP-1.06, 30/80 Elliptical Geom.(3:1), 0.25 width, Injection Rate 1 bbl/ft, 3 cp SPE

35 Transport of ULW 1.05 ASG Proppant 14/40 mesh; 4 cp slick water

36 Emerging Proppant Technology 20 mesh 1,000 psi Partial monolayers exhibit open areas around and between particles increasing the conductivity of the propped fracture Adapted from SPE-1291-G,

37 Conductivity vs. Closures Stress Proppant Packs vs. Partial Monolayer Conductivity (md-ft) Closure Stress (psi) ULW-1.05, 0.02 ppsf 20/ ppsf 20/ ppsf 20/ ppsf 40/ ppsf SPE

38 Emerging Proppant Technologies Stronger, more thermally stable, ultra-lightweight proppants to improve transport and conductivity First generation: 200 o F / 5,000 psi Current generation: 240 o F / 7,000 psi Next generation: 275 o F / 8,000 psi 39

39 Emerging Proppant Technologies Proppants with improved ability to mitigate non-darcy flow issues common to high rate and/or multi-phase production Materials to mitigate effects of proppant pack diagenesis (scaling) 40

40 Emerging Fracturing Technology Production Assurance Particulates containing controlled-release additives deployed in fracturing treatments for long-term flow assurance via inhibition of scale, salt, paraffin, or asphaltene deposition Reside within proppant pack and slowly release production chemicals to maintain the conductivity of proppant packs and to prolong the time to needed intervention (> 3 years protection experienced) 41

41 Emerging Proppant Technologies Ultra-high strength proppants for deep well applications (+20 kpsi) High strength proppants with reduced abrasive properties to protect hardware in high rate, low viscosity fluid applications 43

42 Emerging Proppant Technology Smart proppant to allow mapping of conductive fractures Live or activatable particles dispersed within proppant pack Once placed, can be located within reservoir for identification of the conductive fracture geometry and azimuth. Fracture width can be estimated from frequency 45

43 Summary Hydraulic fracturing of unconventional reservoirs has resulted in significant shifts in the fracturing materials employed, most significantly to lower viscosity fluids and smaller proppant size. 47

44 Summary Evolution of fracturing materials is ongoing to effectively satisfy the developing needs of unconventional resources stimulation Innovation of fracturing materials is occurring to effectively fracture in the everincreasing extremes of reservoir thermal and stress 48

45 Hydraulic Fracturing Materials: Application Trends & Considerations Harold D. Brannon BJ Services Company Thank You! Questions??? Society of Petroleum Engineers Distinguished Lecturer Program 49