Drilling Mud Fundamentals for Barnett Shale Derrickmen

Transcription

1 Drilling Mud Fundamentals for Barnett Shale Derrickmen Douglas Cearley SPE, AADE, SPWLA

2 Types of Drilling Fluids Fresh water mud Salt water mud Brine and cut brine Oil based mud Air Nitrogen

3 Purpose of Drilling Fluid - CCCP Cool and lubricate the drilling bit Convey cuttings to the surface Control underground pressure Oil Gas Salt Water Preserve and protect the hole

4 Mud Properties Fresh Water Mud

5 Mud Weight Mud Weight Measured in pounds per gallon In early days a gallon bucket of mud was hung from a spring scale or cotton scale Now a special balance beam scale is used Water weighs 8.33 pounds per gallon Mud Weight X Depth X.054 = Hydrostatic Pressure

6 Funnel Viscosity Viscosity is resistance to flow It is measured in how many seconds it takes for one quart of mud to flow through a Marsh funnel. The tube in the bottom of the funnel must be clean for a reading to be accurate The viscosity of fresh water is 27 seconds per quart

7 Ph Ph is a measure of the acidity or alkalinity of a liquid It ranges from 1 to 14 1 is completely acidic 14 is completely alkaline It is measured with a Ph strip Fresh tap water has a Ph of 7

8 Chlorides Amount of Chloride Ions (From Salts) Measured in parts per million (ppm) ppm is fresh water ppm is brackish water Above 3000 ppm is salt water Above 3000 cuttings can t be disposed of at simple mud farm Above ppm interferes with mud properties; may have to switch to salt water gel Above ppm dual induction log doesn t work properly

9 LCM Lost Circulation Material Measured in pounds per barrell Many different kinds: Cottonseed hulls Cedar fiber Paper Nuts Mixtures If hydrostatic pressure exceeds bottomhole pressure in a permeable formation, the hole will take a drink ; if this continues you will knock the bottom out (lose all return).

10 Water Loss Also known as API filtrate Measured in milliliters of filtrate per 30 minutes across a filter press A low water loss keeps the various water sensitive formations from swelling In this area, a low water loss needs to be kept through the Pennsylvanian shales and through the Barnett itself

11 Other Properties A number of other mud properties are measured with the rheometer and other special tools belonging to the mud engineer. They are explained at the next level of instruction.

12 Materials These are explained in the order in which they are used.

13 Water Water is used to drill The surface hole The first part of the vertical hole (down to four or five thousand feet, depending on instructions and hole conditions) Properties of water Weight 8.33 pounds per gallon Funnel viscosity 27 seconds/quart Ph of 7 Chlorides should be less than 1000 ppm

14 Sweeps When drilling with water you will be using sweeps to clean the hole Lime and Gel Built in the pill tank, otherwise known as the sweep pit. Send about one foot down every 90 feet (our tank holds 150 bbl above the suction when full). This will be different on other rigs about a 40 bbl sweep is standard. Polymer (Stardrill AP) when using Ambar Sent through the suction pot halfway between lime and gel sweeps

15 Gel Fresh water gel Rock name = Bentonite Mineral name = Montmorillinite It is a clay that forms much of western Wyoming; when mixed with water it forms mud It began its existence as volcanic ash, then weathered to a clay

16 Gel Builds viscosity Decreases water loss Together with water, it forms the colloid which into which the other chemicals are mixed

17 Lime Lime is Calcium Hydroxide It is a strong base and will burn your skin It raises Ph and releases Calcium Calcium thickens the mud (raises the funnel viscosity) Higher Ph thickens the mud (raises the funnel viscosity)

18 Polymer A polymer is a synthetic substance which has molecules with very long chains; many are a product of guar gum, a bean grown and processed in Vernon, Texas In water, the Stardrill AP forms a sticky slug which pushes cuttings ahead of it as it comes back up the annulus

19 Soda Ash Soda ash is a water softener We have it on location only in case we drill into some salt water flow It is not to be used during mudding up as in many places, since our water supply here is soft Do not confuse it with caustic soda

20 Sodium Bicarbonate Sodium Bicarbonate is common baking soda It is sometimes added when drilling cement, in order to lower the calcium level Drilling cement releases calcium and thereby thickens the mud It may not always be on location

21 Caustic Soda Caustic Soda is Sodium Hydroxide, an extremely strong base Always wear rubber gloves, apron, safety glasses, and face shield when handling Mix it through the caustic barrel only It is used to raise Ph Higher Ph gives greater viscosity Higher Ph protects against metal corrosion Drill Pipe Pits

22 Barite Barite is barium sulfate, a naturally occurring mineral It is used to increase mud weight For hydrostatic control of both fluid pressure and rock pressure To keep from blowing out (Northern Division) To support the hole (Southern Division) For slugging the drill pipe dry

23 Detergent Used in liquid form, it slicks up then hole for use in directional drilling Discontinue use if soap bubbles get bad enough to interfere with the pump Be careful with detergent, do not get on your skin because it is stronger than regular laundry soap

24 Graphite Naturally occurring substance formed when carbon has been subjected to great heat and pressure Used to slick up the hole for directional drilling

25 Nut Plug Ground walnut hulls or pecan hulls Contain a natural oil Serves to slick up the hole for directional drilling Secondarily used as lost circulation material Helps more than you would think

26 Cottonseed Hulls The natural protection of the cottonseed Cotton and cotton are valuable commodities; cottonseed hulls are not Used for lost circulation material Also used to make sweeps more effective Can sour if left in the system too long

27 Startrol An asphalt residue Coats the wall of the hole and makes it easier to get in and out of the same Helps decrease water loss Its effect builds up with usage

28 Alcomer 507 Fast acting effective water loss material Keeps water loss down Expensive

29 Lignite Ground up coal Used to thin the mud Acts relatively slowly Secondary purpose is to prevent water loss Anytime you are building volume, you need to put in some lignite or the viscosity will get too high

30 Chem-vis Synthetic chemical used to make the mud smoother and more homogeneous Mixed when building new volume

31 Aluminum Stearate Same chemical as in a shaving pencil Mixed with diesel, it is used to degasify the mud when it is fluffed with bubbles of gas or air