The Development and Evaluation of A Set of New Lost Circulation Material

Conventional lost circulation materials (LCM) have some "deficiencies", for example, the particles of mineral LCM have too big density and are too brittle, thus it is easy for the particles to settle down in drilling fluids, and to crush when the formation fractures are closing. The particles of plant LCM have densities that are too low for them to mix evenly with drilling fluid, and are always float at the top of the LCM slurries. These plant LCM become soft at HTHP conditions, no longer suitable for stopping mud losses. Flake LCM, such as seashells and mica, are also too brittle and the mouth of the opening of fractures are easy to be covered by these flake LCM. In subsequent operations, the flakes are eroded away, inducing mud losses to occur again. To solve these problems, a series of new LCM, the LCC series, have been developed using special techniques. In the LCC series, the LCC100 has densities adjustable between 1.30-2.30 g/cm³, and the ratio of particles broken at 25 MPa is less than 10%. After hot rolling in NaOH solution with pH 12, no obvious changes in the strength of the particles have been found, meaning that LCC100 has good pressure resistance, temperature resistance and high pH tolerance. LC200 is an LCM that is both ductile and rigid. LCC300 can make its way into fractures under pressure, strengthening the plugging and sealing of mud loss channels. It has been demonstrated that LCC series are effective in controlling mud losses into fractures and pores; they remain their integrity at a pressure of 7 MPa on API LCM tester. Oil base or water base LCM slurries made with LCC series can stand 20 MPa on HTHP LCM tester (with wedge-shaped fractures) at 150℃, without being pierced, and the pressure can be stabilized at 19.8 MPa.