Drilling waste generated during development of oil and gas offshore and onshore fields are required to be disposed of in a responsible and environmentally friendly manner. The remoteness of such environments, coupled with the ever-tightening environmental regulations and then green operation initiatives of operators, can create significant economical, logistical and regulatory challenges. The subsurface drilling cuttings reinjection becomes the preferred option allowing oil and gas operators to achieve zero discharge which can meet the most stringent environmental standards. To prevent all possible injection issues that were experienced earlier in the industry globally (early 1990's), a novel "design, execute, evaluate approach was introduced, this enables us to deliver reliable, single sourced start to finish solutions Subsurface drilling waste injection has been and continues to be used on several offshore projects where many millions of barrels of waste have been injected in a single well. This has been achieved through the engineering approach "design, execute, evaluate". The design study assesses the subsurface strata and identifies suitable injection zones, with a focus on waste containment assurance. The execution and evaluation phase begins with an initial injectivity test to calibrate all the reinjection modelling completed so far, we then implement real time injections surveillance including advanced pressure analysis as a risk control tool. The key focus is to analyze, identify, and recommend necessary adjustments during injections to prevent injection failure. The studied cases have been operated successfully since their start to date. No injectivity issues have been experienced during drilling waste fluids injections. Several on-time interventions have been made to proactively prevent the well becoming plugged and maintaining surface injection pressures within normal ranges. Recent advances of Real-time data streaming have made big step change improvement in the data delivery process, monitoring pressure analysis. It creates a direct link between the wellsite and worldwide multidisciplinary technical expertise and provides visualization capability at anytime and anywhere to all personnel involved in the project. This step change in monitoring drilling cuttings reinjection operations provides truly "Acquisition to Answer" integrated solution, mitigates the injection risks and enhances the intrinsic value of drilling cuttings reinjection on offshore development projects. This paper shares the experience and the success of subsurface drilling cuttings reinjection where wastes are injected for final and responsible disposal. The offshore field cases are presented to illustrate the value of the recent technological advances along with best practice guidelines and recommendations for safe and economical disposal of drilling waste fluids to achieve true zero discharge results.

A unique invert emulsion fluid (IEF) weighted up with treated micronized weighting agent (MWA) slurries has been developed and successfully implemented in the field as a completion and testing fluid. The utilization of this unique IEF by design allowed the fluid properties to be lower on viscosity and superior suspension characteristics, which allowed for thermally stable fluid and provided excellent downhole hydraulics performance. Much of the earlier development and deployment of this type of IEF was focused on drilling for sections in narrow mud weight and fracture gradient windows, coiled tubing operations, managed pressure drilling, and extended reach wells. Many of these drilling challenges are also encountered in high pressure and high temperature (HTHP) and ultra-deepwater field developments and mature, depleted fields. Early fluid developments focused on designing the fluids chemistry and physics interactions and the optimization of mineralogy of the weighing agent used. There was also some concern on variability of the results seen on the return permeability as well as standard fluid loss experiments. The paper describes the laboratory and field and rigsite data generated while using the MWA in IEFs during completion operations with a client in India. The paper will briefly describe the laboratory work before the application and the associated results observed on the rig site. It will also outline all the challenges which were faced during the execution and mixing of the MWA IEFs. Each separate operation required a high-density reservoir fluid solution above 15.5 ppg [1.85 sg]. Because corrosion, sag potential, and scale were the operator's main concerns, a solids-free brine or other type of weighting agent (for e.g. Calcium Carbonate and/or Tri-Manganese Tetra Oxide) solution was not favored. A high-density IEF designed with MWA allowed us to provide a solution that mitigated against the risks identified in each operation. The thin viscosity profile enabled completion activities to proceed with minimal fluid consumption at surface, reducing the overall environmental impact. The high-density (15.6 ppg [1.86 SG] and 16.2 ppg [1.94 SG]) invert emulsion fluid was designed to minimize sag potential with minimal reservoir damage potential. With a thinner viscosity profile compared to conventional IEFs at equivalent densities, the fluid enabled completion activities with minimal fluid volumes lost over shakers and reduced the environmental impact. The MWA that was used to build the IEF used for drilling and completion fluid enabled maintenance of extremely low-shear rate viscosities when compared to conventional barite-laden fluids. This fluid was used for suspending and abandoning the well in Case Study A, where the reentry and intervention of the well was planned to be after 2 years. After exposure of the fluid in Case Study A, the fluid showed minimum sag after re-entry of the well and the intervention activities were done without any problems. Case Study B showed that the fluid was mixed to the density of 16.2 ppg and was used to perforate and test two different zones. The bottom hole static temperature (BHST) reported were 356 degF (180 degC) for Case Study A and 376 degF (191 degC) for Case Study B respectively. The paper attempts to show the effects of using this alternative weighing agent as a completion fluid instead of a high-density solids-free brine or other solids-laden high-density brines and the associated success, which could be managed if the fluid design is carefully planned.

The use of micronized weighting agents, in multiple operations, have become more commonplace over the years, with current applications now going far beyond their targeted original purpose of reducing pressure losses in extended reach wells. This specific case reports the development of a fit for purpose system engineered to tackle multiple challenges such as: limitation in using heavy density brines composed of bromides in an offshore environment; hydrate suppression under Drill Stem Test (DST) conditions; weighting agent sagging control; plugging of downhole tools due to heavy solids loading; proper pressure transmission for downhole tools activation; and formation damage prevention. The operation involved the following steps: 1 - development of a Water-based Micronized Weighting Agent Fluid System (WBMWAFS), laboratory testing, simulation evaluation and testing validation for all target properties; 2 - development of an appropriate DST approach with the usage of a designed set of explosives to minimize formation damage and the interaction of the DST fluid with such cargos; and 3 - the evaluation of the overall system performance in order to validate the integrated approach used to design such solution. The DST results indicated that the WBMWAFS is capable of delivering all the technical requirements for a trouble-free operation, with no significant register of weighting agent sag, hydrates or with any variation in fluid properties, whilst enabling a DST operation that demonstrated a negative skin damage during the clean-up period and no damage associated with the WBMWAFS. The WBMWAFS performance opens the possibility of the application of this type of fluid as a replacement for high-density clear brines in many challenging environments.