Expenses for drilling represent 25% of the total oilfield exploitation cost. Drilling fluids represent 15 to 18% of the total cost of petroleum well drilling operations. The main drilling fluids problem is the loss into formations with severe drilling induced fractures or natural fractures and vugs. Prevention or mitigation of severe lost circulation is a main challenge while drilling in these formations where conventional lost circulation materials (LCM) will not cure these losses. Therefore, specialized treatment using fracture seal materials (FSM) is required when drilling through these troublesome formations.
In this study, two superior fracture seal materials made from crushed date palm seeds and shredded waste car tyres were tested at laboratory for its ability to seal artificially fractured cores under High Temperature High Pressure (HT-HP) conditions. For this purpose, the conventional 500 ml HT-HP API filter press was modified to accommodate an artificially fractured core plug of length and diameter equal to 38.1 mm (1.5 inch) instead of the ceramic disc.
Using the HT-HP filter press modified in this study, spud mud with mixtures of either crushed date palm seeds or shredded waste car tyres of different grain sizes proved its ability to completely seal the artificially made fracture in the test core samples at overbalance pressures up to 1000 psi and temperatures up to 90°C. In addition to its superior ability to seal fractured formations, the date palm seeds material is cheap, locally available in commercial quantities, environmentally friendly material and easy to crush into various required grain sizes. In addition to its superior ability to seal fractures under conditions up to 90°C and 1000 psi, the utilization of crushed waste car tyres in drilling operations and other industrial applications can protect the environment from many hazards.
Routine drilling fluids filtration measurements are performed on a filter paper using either the API filter press (100 psi and 25°C) or the HT-HP filter press (175 ml or 500 ml). Alternatively, HT-HP filtration can be performed on a ceramic disc as shown in Fig. 1. Filter papers or ceramic discs are used to simulated rock matrix in non-fractured and non-vuggy formations. Several attempts have been performed to investigate the effect of various fluid loss control materials (LCM) on sealing formations with high permeability and/or micro induced or natural fractures.
