An Improved Method for Grinding and Reinjecting of Drill Cuttings

Abstract

SPE and IADC Members Abstract A successful reinjection of oil-wet drill cuttings has been performed on the Norwegian Gullfaks Field. The reinjection was carried out in the annulus between two casing strings through a wear-protected wellhead. An effective way of grinding cuttings and mixing slurry by use of a new patent pending method known as SMACCC - Statoil Method for Autogenous Crushing and Classifying of Cuttings has been developed. The paper discusses reservoir aspects and presents simulated fracture geometries as a result of rock mechanical and slurry in-put property data. Further, the paper describes a 1000 hour wear test, involved equipment, and gives a derived formula describing wear from sand slurries on internal wellhead components. Introduction The basic background to the cuttings reinjection project wasStatoil's environmental policy to cause the least possible pollution of the environment, andthe company's policy to develop technologies and concepts meeting low crude prices. The increasing demand for highly deviated and longer wells currently necessitates the use of oil-based mud, which is neither permitted to be discharged into the sea nor to be burned. With newly realized environmental concerns, about disposal problems for drill cuttings and drilling solids residue for oil based mud systems, several new disposal methods are currently being considered and investigated by the oil industry. Since 1988, Statoil has reduced the use of oil-based mud by about 95% on the Gullfaks Field. The project of reinjecting cuttings, waste mud and oily waste water from drilling was a following-up project to virtually eliminate the discharge of oily waste from Statoil's drilling and production platforms. As of November 1st 1992, a total of 6500 Sm (40880 BBL) of waste drilling fluids and cuttings have been reinjected into shallow formations on the Gullfaks Field. Reinjection of cuttings by use of the new crushing and mixing system is now planned on several Statoil platforms in the North Sea. This paper discusses simulated reservoir and rock mechanical data together with fluid/slurry properties in conjunction with down-holedisposal operations describes a 1000-hour combined wellhead and centrifugal pump sand erosion test. An equation relating erosion to velocity and sand concentration is given. describes the size and capacity of the new SMACCC system, including an improved and wear-resistant centrifugal pump presents actual field test data and performance analyses for offshore disposal operations RESERVOIR MODELLING AND SIMULATION RESULTS General Considerations Subsurface injection is a world wide common method of waste disposal, and many injection wells have been operating for years with massive volumes of material being injected. The major difference between such "normal" disposal operations and disposal of drilling cuttings and impure mud is the high percentage of solids to be injected, with the corresponding requirement for injection above fracture closure pressure - e.g. it will be necessary to open and probably extend hydraulic fractures and/or open and extend existing natural fractures. P. 773^

Feeling the Pulse of Drill Cuttings Injection Wells—A Case Study of Simulation, Monitoring, and Verification in Alaska

“…This value is consistent with values used in other studies and with laboratory measured fluid loss data on core samples (Willson et al 1999). Elsewhere, cuttings slurry leakoff tests into highly permeable sands have suggested a leakoff coefficient of 0.004 ft/√min for slurry injection (Sirevag and Bale 1993;Moschovidis et al 1993;Willson et al 1993;Guo et al 2000). A value of 6×10 −5 ft/√min was assumed in the overlying shalier formations (Sirevag and Bale 1993;Moschovidis et al 1993;Willson et al 1993;Guo et al 2000;Willson et al 1999).…”

“…While drill cuttings injection projects have been operated worldwide since the early 1990s (Abou-Sayed et al 1989;Malachosky et al 1991;Sirevag and Bale 1993;Moschovidis et al 1993). They were generally small in volume.…”

Investigation of Drill Cuttings Reinjection: Environmental Management in Iranian Ahwaz Oilfield

“…Over time, environmental regulatory requirements have become stricter, drilling and mud system technologies have advanced, and many companies have voluntarily adopted waste management options with more benign environmental impacts than those used in the past. Drill cuttings reinjection (DCRI) operations started in the late 1980s with small volumes of drill cuttings slurry using either tubular or annular injections (Abou-Sayed et al, 1989;Louviere and Reddoch, 1993;Malachosky et al, 1993;Sirevag and Bale, 1993;Willson et al, 1993;Moschovidis et al, 1994). However, as more experience was gained through these lower volume waste disposal operations, drill cuttings injections have been operated in several parts of the world as an economical solution for drilling waste disposal (Baker et al, 1999;Schmidt et al, 1999;Guo et al, 2003).…”

“…The rheological characteristics of cuttings slurries have been commonly represented by a non-Newtonian power law relationship. The power law indices vary significantly (Sirevag and Bale, 1993;Willson et al, 1993Willson et al, , 1999.…”

Challenges for Monitoring and Verification of Drill Cuttings Reinjection Performance

“…1,2 By early 1990s, drill cuttings injections have been operated in several parts of the world as an economical solution for drilling waste disposal. [3][4][5] By the end of 2001, in terms of disposal volumes for drilling waste, Alaska has injected the largest volumes (10 to 14 x 10 6 barrels) in one well, 6-7 followed by Canada. The North Sea has several projects that have injected between 0.25 and 2.0 x 10 6 barrels of waste in each well.…”