McEllhiney Distinguished Lecture Series in Water Well Technology

Transcription

1 National Ground Water Association presents the McEllhiney Distinguished Lecture Series in Water Well Technology sponsored by the National Groundwater Educational Foundation with a grant from the National Ground Water Association by Hank Baski

2 Experience Hank s Guide to Wellness Builds On 40 Years Of: Drilling Started in water well business while in high school Helped to build a cable tool drilling rig for the family drilling business in Northern Minnesota Moved business to Pueblo, Colorado Consulting in Ground Water Hydrology Based in Denver, Colorado Projects nationwide Manufacturing Recognized need for ground water tools Decided to develop products: pitless units, inflatable packers, and downhole flow control valves (currently seven patents on these) Rev. 1 1 My Motto (I m not an easy boss ): question everything & everyone - including yourself - and be willing to change

3 Overview Commonly believed fallacies hinder optimal development of water wells: The use of clear water as drilling fluid results in the best well Artificial gravel pack is needed for sand-free, high-efficiency wells Step pumping aquifer tests can determine well efficiency Airlifting cannot be trusted for reliable aquifer pumping tests and can air-bind a well New technologies and innovations will impact the water well industry over the next decade: Horizontal wells will play a greater role in water recovery and injection Pricing for larger sedimentary wells will be based on well efficiency instead of footage Unique, new methods for well development will arrive Energy savings will drive widespread adoption of aquifer thermal energy storage Case Study: Development of the Denver Basin Aquifers Question & answer session Rev. 1 2

4 Four Fallacies - Clear Water As Drilling Fluid Fallacy 1: The Use Of Clear Water As A Drilling Fluid Results In The Best Well At first sight, drilling with clear water appears natural and pure In reality, it facilitates the invasion of fines up to 5 feet into aquifer Aquifer protected mud cake Drill hole with bentonite mud cake Aquifer protected Better: use of bentonite and other drilling muds forms mud cake, retaining fines and enabling subsequent development of naturally developed, efficient wells Aquifer invaded by fines mud/sediment cake Drill hole with clear water mud/sediment cake Aquifer invaded by fines Rev. 1 3

5 Four Fallacies - Artificial Gravel Pack Mandatory Fallacy 2: Artificial Gravel Pack Is Needed For Sand-free High-efficiency Wells Traditional dogmatic belief: gravel pack is needed in most unconsolidated and semi-consolidated formations (on left) Best solution (top right): natural gravel pack development using drilling mud, jetting and high-performance wellscreen Rev. 1 4 Artificial Gravel Pack Aquifer protected mud cake Aquifer invaded by fines mud/sediment cake bentonite large slot screen large slot screen clear water narrow slot screen narrow slot screen Natural Gravel Pack void void Aquifer protected Aquifer invaded by fines

6 Four Fallacies - Artificial Gravel Pack Mandatory How Well Screen Types Affect Jetting Development Continuous Slot Screen Bridge Slot Screen Slotted Pipe Louvered Screen Source: Groundwater and Wells by Fletcher G. Driscoll / Johnson Screen (Weatherford), Second Edition Rev. 1 5

7 Four Fallacies - Artificial Gravel Pack Mandatory Naturally Developed Well (No Gravel Pack) Source: Advertisement by Johnson Screen (Weatherford) Rev. 1 6

8 Four Fallacies - Step Pumping & Well Efficiency Fallacy 3: Step Pumping Aquifer Tests Can Determine Well Efficiency Related fallacy: constant rate pumping is best for aquifer tests First, a refresher on concepts, terms, and definitions: What kinds of pumping aquifer tests are there? Transmissivity, coefficient of storage, and other aquifer & well characteristics What is well efficiency? Then, a pragmatic perspective on what pumping aquifer tests are most economical and easiest to perform Rev. 1 7

9 Four Fallacies - Step Pumping & Well Efficiency Groundwater and Wells Is An Invaluable Bible Rev. 1 8

10 Four Fallacies - Step Pumping & Well Efficiency The Bible Compares Two Kinds Of Pumping Tests Pumping Tests Principle Typical Analysis Constant Rate Install one or more observation wells at appropriate distance from the pumping well Pump at constant rate for 24 or 72 hours, depending on type of aquifer Take periodic drawdown measurements from the pumping and observation wells Time-drawdown graph in semilogarithmic plot Distance-drawdown graph in semi-logarithmic plot Step Drawdown Pumping rate is increased in steps at regular intervals Example: 100 gpm for 2 hours 200 gpm for next 2 hours 300 gpm for next 2 hours and so on Take data in both pumped and observation wells Time-drawdown graph in semilogarithmic plot Distance-drawdown graph in semi-logarithmic plot Source: Groundwater and Wells by Fletcher G. Driscoll / Johnson Screen (Weatherford), Second Edition Rev. 1 9

11 Four Fallacies - Step Pumping & Well Efficiency Early Time Data Is Almost Worthless In Most Cases The initial S-shaped component is due to casing storage In most cases, specific capacity is more reliable than slopes (semi-log) or matchpoints (log-log) of aquifer test data for calculating transmissivity 10% Rule: It is not necessary to have an uninterrupted aquifer test. I have found that a shut-down equal to about 10% or less of previous pumping time is OK. Drawdown 0 Casing Storage Effect Specific Capacity [gpm/ft] = Pumping Rate [gpm] Drawdown [feet] B ,000 A C log time [min] Rev. 1 10

12 Four Fallacies - Step Pumping & Well Efficiency Comparing Theoretical and Actual Drawdown... Source: Groundwater and Wells by Fletcher G. Driscoll / Johnson Screen (Weatherford), Second Edition Rev. 1 11

13 Four Fallacies - Step Pumping & Well Efficiency... Leads to the Concept of Well Efficiency Ground Level Distance - Drawdown Graph in Semi-log Plot Static Water Level Pumping Water Level Actual Drawdown Theoretical (Extrapolated) Drawdown assuming well efficiency remains the same over time Distance from center of well [casing radii] Well Efficiency [%] = Theoretical Drawdown [feet] Actual Drawdown [feet] Rev. 1 12

14 Four Fallacies - Step Pumping & Well Efficiency Turbulent And Laminar Flow Components In Step Drawdown Tests Do Not Measure Well Efficiency Many investigators and practicing engineers have (erroneously) equated turbulent flow with well inefficiency They falsely assume that the laminar head loss is the ordinary aquifer loss and that the turbulent head loss component is strictly the inefficiency drawdown component due to aquifer damage and head loss through the well screen However, we have seen efficient wells which exhibit some turbulent flow - and also seen inefficient wells where the excess head loss due to formation damage and flow through the screening device is essentially laminar! Rev. 1 13

15 Four Fallacies - Step Pumping & Well Efficiency Not Mentioned Even In The Bible : There Are More Than Two Kinds Of Pumping Aquifer Tests 1. Constant Rate, with step drawdown considered a variant 2. Constant Drawdown, where one records the pumping rate required to maintain a given drawdown 3. Variable Discharge & Drawdown (e.g. using air-lift pumping) Vertical Axis Variables: 1. s (drawdown) 2. 1/Q (gpm) 3. s/q Casing Storage Effect ,000 log time [min] Air-lift pumping proves the cheapest & most effective aquifer test Rev. 1 14

16 Four Fallacies - Airlifting Cannot Be Trusted Fallacy 4: Airlifting Cannot Be Trusted For Reliable Aquifer Pumping Tests And Can Air-bind A Well Who here has experienced air-binding first-hand? Reasons why people have opposed use of air-lifting Unwarranted fear of air-binding Air-lift pumping tests force you to think of formation pressures rather than water levels. But this results in better data collection, analysis, and understanding of the aquifer regimes. Lack of easily-accessible, broad-based analysis methods Well development with air proves advantageous Surge block development can be improved by simultaneously using air. While surging, air can be used to pump out water and fines. For stubborn wells, high-pressure air-jetting loosens up and removes drilling mud and fines Rev. 1 15

17 Four Fallacies - Airlifting Cannot Be Trusted Airlifting: Principles, Definitions & Example Principles of Operation: 1. Aerated column is lighter than submergence (think of a lake and then progress to a well) 2. Aerated column during pumping + friction loss = submergence 3. Empirical relationships are state-of-the-art. Probably it s impossible to derive and/or calculate accurate formulas describing requirements and performance of all air-lift operations. Key Definitions: Pumping Submergence PS % = (APD - PWL) / APD APD = Air Pipe Depth PWL = Pumping Water Level Static Submergence SS psi = APD - SWL APD = Air Pipe Depth SWL = Static Water Level Rev Example Specifications: 8 inch borehole or well pipe I.D. 2 inch air pipe I.D. 40% pumping submergence 1900 cfm air compressor delivery 450 gpm air-lift pumping capacity Sources: Why Airlift Pumping Tests by Hank Baski (Feb 79), Baski Inc. Catalog #6

18 Four Fallacies - Airlifting Cannot Be Trusted Approximate Air-Lift Pumping Capacities Borehole or well Air Pipe Pumping Submergence % Pipe Tube Nominal Actual Air Compressor Delivery Size OD 10% 20% 40% 60% 80% (inch) (inch) (gpm) (gpm) (gpm) (gpm) (gpm) (cfm) 3/8 1/ /2 3/ /4 1/ / /2 1/ Pipe Pipe Nominal Nominal Size Size 2 1/ / / / / Air Compressor Requirements Pressure rating [psi] must be 20% greater than the Static Submergence [psi]. Volume rating [cfm or cubic feet per minute] must approximate values from this table for hydrology testing: If the water production surges, i.e. varies in gpm rate, then a GREATER cfm is needed. On the other hand, well development by air-lift pumping is enhanced by surging; therefore, a LOWER cfm is desired for part of the development period. Do not significantly exceed the listed air delivery rate [cfm] as this will dramatically increase the friction loss in the annular area, causing the water production to decrease to the point where if too much air is introduced, no water will be produced. NOTE: 1 foot of water = psi 1 psi = 2.31 feet of water Rev. 1 17

19 Four Fallacies - Airlifting Cannot Be Trusted Airlifting: Evolution, Design, And Advantages Air-lift pumping was used before centrifugals At least 80% of the aquifer tests that I have conducted used air-lift pumping Advantages include: Readily available equipment (difficult to obtain conventional pumps for well diameters < 4 inch or for productions > 2,000 gpm) Dependability (no moving parts so high sand pumping rates are no problem, no expensive components to lose) Lower cost, normally... There are some disadvantages: Limited by minimum submergence requirements Not well understood Air compressor availability may be limited Rev. 1 18

20 Four Fallacies - Airlifting Cannot Be Trusted Airlifting Advantages (cont.) Versatile: anticipated well production does not need to be known - but it does need to be known for conventional pumping tests Suitable for both small diameter (1/2 or less) and large wells No practical depth limitation Very easy to obtain pumping and non-pumping water level measurements Can produce approximately twice as much water from a given well diameter Practically eliminates casing storage effects Well suited for conducting in-hole flow meter surveys during pumping. The results are a testing necessity for in-situ leaching or mining, and most valuable & powerful in describing aquifers. Rev. 1 19

21 Four Fallacies - Summary Why Fallacies Live On ( Psychology Behind Fallacies) Webster s defines: Fallacy: a false idea Myth: an ill-founded belief held uncritically, especially by an interested group Overcoming human resistance to change is very difficult as one must admit internally that one has been making mistakes in past It s not so much the not knowing that contributes to the sum of human ignorance as it is the knowing so much that ain t so. Rev. 1 20

22 Four Forecasts Novel Solutions For Unmet Needs Drive Forecasts Sense for unmet needs got me into business Know more novel solutions than have resources Breakthroughs from all sources give rise to new trends for markets & technology of ground water industry: my forecasts Why should you care? Unmet needs, novel solutions, and/or resulting improvements may well impact your business too! Rev. 1 21

23 Four Forecasts - Horizontal Wells in Recovery & Injection Forecast 1: Horizontal Wells Will Play A Greater Role In Water Recovery And Injection Unmet need: ever increasing demand for water of all kinds (potable, irrigation, industrial) in a time of dropping water levels Solution: There is plenty of water down there Horizontal well completion enables more effective aquifer draining Case study: Denver basin Rev. 1 22

24 Four Forecasts - Horizontal Wells in Recovery & Injection Two Pumping Structures (Wells) In A Single Aquifer Rev. 1 23

25 Four Forecasts - Horizontal Wells in Recovery & Injection The System Can Be Extended to Three, Seven, Or More Pumping Structures Rev. 1 24

26 Four Forecasts - Well Efficiency, Footage & Pricing Forecast 2: Pricing For Larger Sedimentary Wells Will Be Based On Well Efficiency Instead Of Footage Recall definition of well efficiency as actual / theoretical drawdown (related fallacy: 100% well efficiency is as good as it gets) Unmet need: today the contractor with lowest $/foot bid gets job, and customers end up with too many, inefficient wells Solution: Customer pays for well efficiency based on formula, e.g. only 70% of bid rate if well only 70% efficient Specification consultant decides casing size & material, screen size & material, collapse strength of tubulars, depth, grouting intervals, straightness, plumbness, and suspended solids limits after development. Also decides calculated well efficiency with review provisions. Contractor decides all technical aspects of drilling and development: drill hole diameter, drilling fluid, screen, etc. with input from consultants and suppliers. In larger projects, lowest bidder may be awarded 1/2 of all wells, second gets 1/3rd, and remaining 1/6th goes to third-ranked bidder. Rev. 1 25

27 Four Forecasts - Well Efficiency, Footage & Pricing Adoption Will Proceed Gradually, Where Project Conditions Are Favorable Contractors Customers Become more knowledgeable Unit cost for water Factors that influence is reduced adoption of new model: Hydrogeology Ratio of drawdown to pumping depth Production rate Level of fixed and variable (energy) costs More cooperation: less us vs. them negativism between contractors & consultants Consultants High quality wells for customers Raises standards in industry Skilled contractors paid more Unskilled fade away Rev There will be new roles for consultants: Specification responsibility Advising to contractors Arbitrators of well efficiency calculation

28 Four Forecasts - New Methods in Well Development Forecast 3: Unique, New Methods For Well Development Will Arrive Unmet needs: Inadequate development of new wells In Aquifer Storage & Recovery (ASR): ways to deal with suspended solids, bacterial growth, precipitation, and entrained gas Solutions include: Underbalanced drilling Chemicals Simultaneous high-pressure jetting & pumping, air jetting at 1,000+ psi Imported methods, e.g. ultrasonics Patented methods from oilfield: pulsing technology Airlifting with variations Combinations, e.g. pumping + sonic, airlifting + surge blocks, jetting + surge block + pumping + sonic + chemicals Rev. 1 27

29 Four Forecasts - New Methods in Well Development The Bible Down Under Rev. 1 28

30 Four Forecasts - New Methods in Well Development From Australia: Combined Jetting And Air-Lift Tool Rev. 1 29

31 Four Forecasts - New Methods in Well Development From Australia (cont.): The Valve Screen Plunger And Development Of Long Screens With Air Rev. 1 30

32 Four Forecasts - Aquifer Thermal Energy Storage Forecast 4: Energy Savings Will Drive Widespread Adoption Of Aquifer Thermal Energy Storage Unmet need: effective method for using aquifers as economically (and environmentally) attractive heating & cooling reservoirs, especially valuable in temperate zones Solution: successful Dutch projects, also attempted in Canada ASR well technology applies directly to ATES Total energy balance on a yearly basis requires full cooperation between heating & cooling engineers and ground water hydrologists winter winter summer heat exchanger summer Cold Water Rev Warm/Hot Water

33 Case Study: Introduction A Practical Illustration - Denver Basin Development Since 1968, some of you may have seen me present issues surrounding nontributary ground water, aquifer storage & recovery (ASR), and the Denver basin: The Complex, Yet Simple, Issue of Non-Tributary Ground Water (1981) The Complex, Yet Simple, Issue of Denver Basin Nontributary Ground Water at the Colorado Water Congress, Workshop on Nontributary Ground Water in Denver, Colorado (October 29, 1986) Design and Material Considerations for ASR Systems at AWPCA in Prescott, Arizona (July 20-21, 2000) The Denver Basin and ASR at the American Groundwater Trust in Lakewood, Colorado (June 13, 2003) Rev. 1 32

34 Case Study: Introduction From Pleasantville to Panicsville: Media Propagates Crises, Poor Information, And Bad Solutions WATER BILL: $3 BILLION (Rocky Mountain News 11/26/03) RUNNING DRY (four-part series in RMN 11/22-26/03) BIG STRAW FEASIBLE, COSTLY (Denver Post 11/18/03) WATER DIET FOR CALIFORNIA (RMN 10/16/03) Questionable claims attributed to some experts include: Parts of Denver could begin running out of usable underground water from their main source within 10 to 20 years Water in some areas could become too expensive to pump Colorado needs $15-billion, 27-year Big Straw project to transport millions of gallons of Western Slope water daily across mountains Rev. 1 33

35 Case Study: Introduction Experience Shows Projects (Good, Bad & Ugly) Are Entangled In A Web Technical (1950 s & 60 s) Political (1990s) Legal (1970s) Dogmatic Beliefs (2000) Environmental (1980s) Economic (1970s) Timing (1970s) Rev. 1 34

36 Case Study: Denver Basin Development Technical Issues Used To Get Primary Consideration Technical Issues: Vertical / Horizontal Well Completions Casing & pump column material considerations Technical (1950 s & 60 s) Well Development Methods ASR Considerations Gotcha s & Future Thoughts Political (1990s) Environmental (1980s) Dogmatic Beliefs (2000) Timing (1970s) Legal (1970s) Economic (1970s) Rev. 1 35

37 Case Study: Denver Basin Development The Denver Basin Comprises Four Main Aquifers Elevation (feet) DENVER BASIN CROSS SECTION Rev. 1 36

38 Case Study: Denver Basin Development Background On The Denver Basin Reservoir Location: the reservoir is ideally situated along the Rocky Mountain Front Range where the high water demand is present Reservoir capacity: 250 to 500 million acre feet (AF) in storage Pumping and artificial recharge capacities are estimated to be at least 1/2 to 1 million AF per year, approximately 450 to 900 MGD Life: The basin will be utilized as a reservoir for the foreseeable future Existing water in storage will be pumped for the next 500 years Aquifer Storage & Recovery (ASR) started in 1992 at Highlands Ranch (Centennial Water & Sanitation District). As the reservoir is drawn down, ASR is expected to expand throughout the basin ASR in this reservoir will allow for a more economical and efficient water supply, especially in those areas of higher demand and during times of long term drought Rev. 1 37

39 Case Study: Denver Basin Development Water Levels Will Stop Falling At 30 Feet/Year Once They Reach The Top Of An Aquifer Example: Artesian Coefficient of Storage 1. Bulk modulus of water 2. Reduction of aquifer thickness Water Table Specific Yield: Porosity = Specific Retention plus Specific Yield Typical value = feet of water level change correspond to < 0.05 feet of water recovered Normally = correspond to feet! Media Fallacy: When Conventional Wells Run Dry, The Aquifer Is Doomed Rev. 1 38

40 Case Study: Denver Basin Development Ground Water Diversions (In The Denver Basin) Rev. 1 39

41 Case Study: Denver Basin Development Cost To Produce Denver Basin Ground Water Rev. 1 40

42 Case Study: Denver Basin Development 20,000 Year Future For Denver Metro Water Demand & Supply (Remember, You Saw It Here First...) Rev. 1 41

43 Summary - Recap Development of the Denver Basin Aquifers Illustrates Some Fallacies Roots & Forecasts For The Industry,... Commonly believed fallacies hinder optimal development of water wells: The use of clear water as drilling fluid results in the best well Artificial gravel pack is needed for sand-free, high-efficiency wells Step pumping aquifer tests can determine well efficiency Airlifting cannot be trusted for reliable aquifer pumping tests and can air-bind a well New technologies and innovations will impact the water well industry over the next decade: Horizontal wells will play a greater role in water recovery and injection Pricing for larger sedimentary wells will be based on well efficiency instead of footage Unique, new methods for well development will arrive Energy savings will drive widespread adoption of aquifer thermal energy storage Rev. 1 42

44 Summary - Q&A Setup What Fallacies Have You Encountered? Water Witching (works - doesn t work) Cable tool drilling is slow and old-fashioned Geology determines regional groundwater flow Porosity is important Doubling well diameter = 2x well production Well development unnecessary for domestic wells Air drilled wells do not need to be developed Water producing zones are always easily identified when drilling with air Air lines are not reliable or accurate for measuring water levels Pumping clear water means a well is fully developed Rev. 1 43

45 Summary - Q&A Setup Further Trends Impacting Our Industry - Which We May Address In The Q&A Session Groundwater currently considered brackish will become more important as treatment technologies improve & become more economical Technology to maximize use of low production aquifers will increase and become more important Stainless steel and other non-corrosive materials Point of use treatment Additional safeguards Automation Higher pricing for delivered water Application of a vacuum to the casing and dewatered aquifers Rev. 1 44

46 Q&A - Contact Information Please Feel Free To Call For Further Discussion: Hank Baski Baski, Inc. phone: +1 (303) [email protected] Rev. 1 45