It is designed for drilling of unstable terrigenous deposits of the bottom carbon Dniepr-Donetsk Depression, directional drilling, offshoots and horizontal wells.
PIBR-2 provides high quality penetration of pay zone. The permeability damage coefficient is at level that provided buy the use a traditional chlorine-potassium drilling mud. The distinguishing feature of a flushing system PIBR-2 is the use as the basic stabilizer reagent AbramiX® acrylic polymer, which in combination with potassium chloride provides the greatest inhibitory effect.
HISTORICAL REFERENCE
In the 60-70s American researchers has identified the negative role of lignosulfonate reagents in inhibited drilling muds. This discovery was the impetus for the development of inhibited flushing systems, stabilized with high molecular polymeric reagents. PIBR was the first such system in Ukraine and was developed in UkrNIGRI in the early 80s. This system based on the Anilis (synthesized acrylonitrile-lignosulfonate copolymer). PIBR widely used in the areas of the Ministry of Geology of the USSR until the collapse of the USSR, when the supplies of raw materials for the production of reagent Anilis has been stopped. PIBR system for the first time proved the possibility and expediency of an acrylic reagent in inhibited drilling fluids.
ADVANTAGES
- The complete exclusion of an evaporated sulphite waste liquor has dramatically increased the inhibitory properties of the mud due to the attenuation processes of dispergation and hydration.
- Joint inhibitory effect AbramiX® reagent and potassium chloride results in a powerful reinforcing effect on the borehole wall. This allows more than halve the content of potassium chloride in the system without the risk of complications. For laboratory data PIDM-2 containing 1.8-2% KCl has the same inhibitory effect as chlorine-potassium drilling mud containing 3.5-5% of potassium chloride.
- Reducing the potassium chloride content leads to economy of reagents-stabilizers and facilitates interpretation of geophysical data.
- Thermostability PIBR-2 is above 170-180˚C. A distinctive feature of the system is very low HPHT fluid loss at 120-140 ˚C that eliminates special high temperature stabilizers additives.
- High lubricity and anti-sticking properties (Coefficient of mud cake friction at the level of 0.15-0.18 without use of additional lubricating additives). It allows to abandon the use of environmentally hazardous substances, such as oil. The proposed system for all the above items exceed the flushing system on the hydrolyzed polyacrylonitrile base widespread in Ukraine.
LIMITATIONS
- Filtration loss can increase when the concentration of polyvalent ions in the filtrate of drilling mud more than 0.1% due to water inflow or drilling in cement. In such cases, before using the reagent AbramiX® is necessary to make additional treatment of drilling mud by soda ash.
- A side effect of the use AbramiX® reagent is a possible to increase rheological and structural-mechanical parameters of the flushing fluid. This effect is especially strong in the primary treatment and due to pollution drilling mud with cuttings. It is necessary to reduce solid content by mud cleaning or dilution with water.
COMPOSITION AND PARAMETERS OF FLUSHING SYSTEM
Drilling fluid composition:
- AbramiX® - 2-3% (on dry product);
- CMC (PAC) - 0.1-0.2%
- KCl - 3-5% (if necessary, the concentration of KCl can be increased up to 10%);
- Thinning agents: РПС® - 0,1-0,5% combined with coal-alkali reagent or lignosulphonate - 0,3-0,5%;
- Soda ash - up to 0,5% (periodically for admission of multivalent ions);
- Graphite - up to 1% (before casing running);
- Weighting agents (baryte, hematite, chalk, ground limestone) - depending on the desired density;
- Drill cuttings slurry or bentonite - rest.
Parametrs of drilling mud:
- Density - 1160-2300 kg/m3,
- Funnel Viscosity - 50-120 s,
- Gel - 40/60-80/120 dPa,
- Filtration loss - 6-8 cm3/30 min,
- HPHT fluid loss at reservoir temperature and pressure drop 5 МPа - 18-22 cm3/30min,
- pH - 9.5-10.5.
