Prediction and diagnosis of lost circulation in wells
In accordance with aspects of the present disclosure, techniques for predicting, classifying, preventing, and remedying drilling fluid circulation loss events are disclosed. Tools for gathering relevant data are disclosed, and techniques for interpreting the resultant data as giving rise to an actual or potential drilling fluid lost circulation event are also disclosed.
1. A method of diagnosing a cause of a drilling fluid lost circulation event, the method comprising:
recording data regarding: a rate of drilling fluid loss at the time of the event, cumulative drilling fluid losses as a function of drilling depth, borehole material electrical resistivity as a function of drilling depth, a predicted pore pressure at the time of the event, a predicted fracture gradient at the time of the event, leak-off test behavior prior to or at the time of the event, porosity and permeability information of material at an estimated location of the event, a rate of drilling fluid loss at a time after a lost circulation pill treatment, a borehole image, gamma ray emissions of material at an estimated location of the event, a tectonic regime of material at an estimated location of the event, an equivalent circulation density at an estimated location of the event, borehole temperature as a function of drilling depth, drilling fluid salinity, presence of fractures at an estimated location of the event, fault conductivity at an estimated location of the event, drilling fluid gain when drilling fluid is not being pumped, borehole trajectory, and drill bit drag and penetration rate at the time of the event;
classifying, based on the data, the event as at least one of: seepage, borehole breathing, induced axial fracture, induced near-orthogonal fracture, natural fracture, vugulars, and ineffective isolation of casing shoe;
determining remedial measures, based on the classifying, to at least partially cure the event; and
implementing the remedial measures.
2. The method of claim 1 , wherein the measures comprise reducing an equivalent circulation density.
3. The method of claim 1 , wherein the measures comprise pumping a lost circulation pill.
4. The method of claim 3 , wherein the lost circulation pill comprises CaCO 3 .
5. The method of claim 3 , wherein the lost circulation pill comprises filament fiber.
6. The method of claim 3 , wherein the lost circulation pill comprises graphite.
7. The method of claim 3 , wherein the lost circulation pill comprises cement.
8. The method of claim 3 , wherein the lost circulation pill comprises resin.
9. The method of claim 3 , wherein the lost circulation pill comprises cross-linked polymers.
10. The method of claim 3 , wherein the lost circulation pill comprises aerated mud.
11. The method of claim 1 , wherein the measures comprise optimizing drilling fluid salinity.
12. The method of claim 1 , wherein the measures comprise reducing a weight of the drilling fluid.
13. The method of claim 1 , wherein the measures comprise reducing a rate of penetration.
14. The method of claim 1 , wherein the measures comprise increasing a temperature of the drilling fluid.
15. A method of predicting and preventing a potential drilling fluid circulation loss event, the method comprising:
recording data regarding: a rate of drilling fluid loss at the time of the event, cumulative drilling fluid losses as a function of drilling depth, borehole material electrical resistivity as a function of drilling depth, a predicted pore pressure at the time of the event, a predicted fracture gradient at the time of the event, leak-off test behavior prior to or at the time of the event, porosity and permeability information of material at an estimated location of the event, a rate of drilling fluid loss at a time after a lost circulation pill treatment, a borehole image, gamma ray emissions of material at an estimated location of the event, a tectonic regime of material at an estimated location of the event, an equivalent circulation density at an estimated location of the event, borehole temperature as a function of drilling depth, drilling fluid salinity, presence of fractures at an estimated location of the event, fault conductivity at an estimated location of the event, drilling fluid gain when drilling fluid is not being pumped, borehole trajectory, and drill bit drag and penetration rate at the time of the event;
classifying, based on the data, the potential drilling fluid circulation loss event as at least one of: seepage, borehole breathing, induced axial fracture, induced near-orthogonal fracture, natural fracture, vugulars, and casing hole;
determining preventative measures to prevent the potential drilling fluid circulation loss event from occurring; and
implementing the preventative measures.
16. The method of claim 15 , wherein the measures comprise reducing an equivalent circulation density.
17. The method of claim 15 , wherein the measures comprise pumping a lost circulation pill.
18. The method of claim 17 , wherein the lost circulation pill comprises CaCO 3 .
19. The method of claim 17 , wherein the lost circulation pill comprises filament fiber.
20. The method of claim 17 , wherein the lost circulation pill comprises graphite.
21. The method of claim 17 , wherein the lost circulation pill comprises cement.
22. The method of claim 17 , wherein the lost circulation pill comprises resin.
23. The method of claim 17 , wherein the lost circulation pill comprises cross-linked polymers.
24. The method of claim 17 , wherein the lost circulation pill comprises aerated mud.
25. The method of claim 15 , wherein the measures comprise optimizing drilling fluid salinity.
26. The method of claim 15 , wherein the measures comprise reducing a weight of the drilling fluid.
27. The method of claim 15 , wherein the measures comprise reducing a rate of penetration.
28. The method of claim 15 , wherein the measures comprise increasing a temperature of the drilling fluid.