New Technologies for Effective Recycling of Oil Based Mud. Experience of Prirazlomnoye Field
Authors: Dobrokhleb P. , Kozyrev A. , Mishin A. , Voitenko D. , Kireev V. , Krepostnov D. 
Published: October 2017

The vector of the oil and gas industry development shows an intensive increase of investments into drilling. Oil-based mud (OBM), in conjunction with new drilling technologies, which have recently been used primarily in complex wells and offshore, are now becoming an effective solution for mass drilling on land where existing technologies have already been developed and proved to be effective. Nevertheless, these decisions have reached their technological limit and do not allow to obtain the expected returns under the new conditions.

OBM in addition to the unsurpassed drill-in quality, it allows keeping high borehole stability and drilling efficiency. Its advantage is the possibility of re-use and a minimum of wastes. In mass drilling, this reduces its cost and makes it competitive with WBM. This approach has a reverse side - with repeated use of the mud, a fine-solid phase accumulates and rheology grows up at each subsequent well. Control of these processes by standard solids control equipment is practically impossible, as it is impossible to remove the accumulated amount of colloidal phase by traditional mechanical method (centrifugation). An alternative, to some extent, allowing reducing it is dilution, which affects the volume and cost of the OBM.

Currently, a new technology for recycling is the effective solution for controlling solid phase in OBM and the level of ecological danger of drill cuttings: combination of centrifugal drying system for drill cuttings and removal of the colloidal phase by a chemical-mechanical method using a high-performance centrifuge. This solution was implemented as a part of a campaign to drill horizontal wells of lightweight construction at the Prirazlomnoye field of OOO RN-Yuganskneftegaz. Optimizing the well design involves combining two intervals with different gradients of reservoir pressures and fracturing into one. In conditions of high rates of penetration and a requirement to have minimum operations for hole cleaning, this approach imposes significant restrictions on the operating range of equivalent circulating densities and requires careful planning of each element of the drilling system. The application of OBM allows ensuring stability of the wellbore and optimal conditions for operation of bottom hole assembly tools. A narrow range of operational ECD requires stable parameters of mud throughout the drilling process.

The use of recycling technology has made it possible to achieve significant results: Significant decrease of low gravity solids content;Reduction of wastes to the pits;Solids control efficiency increase above 90%;Significant OBM cost reduction (more than 2 times).Stable mud properties while drilling when it is reused several times.

The article describes solutions, achieved results and the way, how in the current conditions of increasing requirements to technology and the increase in the complexity of the wells, integrated solutions for OBM cleaning allow to provide technical, ecological and economic justification of using high-tech and expensive drilling fluids for mass drilling.