Fast drilling, gumbo clay, and traditional solids control equipment activities can result in a number of problems, including:
• High drilling fluid losses due to the particulate control devices.
• A large amount of dispersion.
• High processing fluid volumes necessitate disposal that is tightly regulated to protect the environment.
• Mesh clogging in the solids controls devices on a constant basis.
• The use of computers is becoming more prevalent.
• Due to the screw conveyors being clogged, there is fluid spillage.
• The solids control devices are not properly monitored.
The performance of solids control equipment during drilling operations is influenced by numerous variables. A cascade-style screen arrangement, hydro cyclones, mud cleaners, decanter centrifuges, and a drying shaker make up the standard solids control unit array. The continuous plugging of the mesh in the screens that results from the continuous presence of gumbo-type clay during drilling near surface sections, when coupled with the high rates of penetration characteristic during drilling these intervals, affects the efficiency in handling the circulating volumes.
As advised by the drilling fluids service provider on site, PDVSA-Oriente increased its continuous improvement methods for drilling operations in late 2001 to incorporate solids control optimization. A flowline distributor was added to the return line’s terminus and the principal screens of the solids control system were reconfigured as the optimization procedure was applied to wells dug north of Monagas. Due to the modifications made, there were fewer issues with handling fluids when drilling highly reactive clays.
Selection, capacity, and positioning of the units are influenced by factors like flow volume, drilling fluid type and qualities, rate of penetration, and lithology of the encountered formations. Solids control service providers aim to continuously enhance the machinery and include high-performance components to boost mechanical removal efficiency during drilling based on operational experience.
During the second part of the study, it was determined to get rid of the screw conveyors and dryer shaker due to operational safety concerns and the insignificant advantage they provided.
First Step of Optimization
On wells 1 and 2, phase 1 of the optimization process was started. Although keeping the number of units characteristic of ordinary arrays, a flow distributor at the end of the return line and a linear configuration of the screen array were added. Monitoring SCE performance was restricted to testing effectiveness by mass balance every three days while both wells were drilling. The following outcomes were produced as a result of the changes made during this initial phase:
• Uniformity of the fluid’s distribution across the displays.
• Mesh usage during operation and design optimization.
• Reduction of wasted fluid volume and disposal requirements.
• Enhanced control over SCE performance.
• Cost-cutting in operations.
The data collected were compared in order to establish a technical basis for the use of a dryer shaker. The investigation showed that using the dryer shaker did not improve the operation since, for the most part, the MOC values for the cuttings that were discarded from these units were comparable to those obtained with the primary screens, secondary screens, and primary units.
Second Step of Optimization
In wells 3 through 9, the second stage of the optimization procedure was run. Wells 3, 4, 6, and 7 are in the same field, while wells 5 and 8 are close by. Well 9 is an exploration well that is located in a separate field from the ones described earlier.
The second phase saw the implementation of the new focus, which involved applying an evaluation matrix with the following criteria: fluid density and rheological properties; total solids content (high and low gravity); percentage MOC, in volume and weight; classification of the mesh design; and mechanical removal efficiency. Daily application of the evaluation matrix and execution of retorts were necessary.
Solids control unit
Following the removal of the screw conveyors and dryer shaker from the system, well number three was the first to be dug during this optimization phase. Screens with high performance were used. Continuous records were kept in each well that reflected the variables included in the assessment matrix. The close observation allowed for the establishment and improvement of the SCE and MOC weight ranges of operation in the drill cuttings processing, as well as the validation of the choice to replace the dryer shaker and screw conveyors with high-performance screens with a finer mesh than had previously been used in each of the phases. The direct discharge system, which consists of a series of inclined metal trays, was also part of this phase. Its purpose is to transport the solids discharged from the screens, mud cleaner, and decanter centrifuges to the collector tanks.
It was possible to use finer mesh in the primary mud screens when drilling the near-surface interval with water base fluids due to the SCE’s high performance (average 5.7 “G” power in the mud screens) during the evaluation. The primary units used a 175x175x175 mesh arrangement, and unit 3 in 1 used a 250x250x250 mesh. Previously, drilling these phases with large flow volumes (>900 gpm) using 84x84x50 mesh designs in the principal units and 175x175x175 mesh in unit 3 in 1 had proven to be challenging.
The drilling operation used an optimal mesh design (210210 mesh for the primary units and 250 mesh in the 3 in 1) when drilling the intermediate hole with oil base fluid and where the formation’s predominant lithology is shales. The primary mud screens, which traditionally worked with the 175x175x175 mesh array and 250x250x250 for the 3-in-1 mud cleaner, were optimized by using the same design of mesh described for the intermediate hole during the production interval, where the predominant lithology consists of sandstone and shale lenses.
It has also been able to increase the number of mud screens recommended for drilling as a result of ongoing monitoring. In order to achieve good performance in the solids control units, five primary mud screens were used in wells 3 through 6 and 9 while four primary mud screens were recommended and used in wells 7 and 8.
The above-mentioned improvements enabled the following:
• Elimination of operating hazards and the time delays caused by mechanical and electrical breakdowns.
• Reduction of safety risks connected with the operation of screw conveyors.
• Cost savings related to the solids control process.
• Enhancing the mesh design.
• A reduction in the fluid volume associated with wasted solids. Improved management of the MOC %.
• Determining permissible MOC values, expressed as a percentage of weight.
The quantity and kind of particles in a drilling mud system can have a negative impact on the mud’s characteristics, lower penetration rates, harm drilling equipment, and raise overall drilling expenses. Controlling the solids content of the mud system is a crucial step in creating a drilling program that is both effective and affordable. Dilution and/or displacement of entire mud, settling, and mechanical solids-control devices are the three main techniques for eliminating solids.
The most efficient way to control solids is using equipment. A variety of equipment is available, each of which is built to function as effectively as possible given the features of the specific fluid system and of the drilled solids from the formation. Systems that are properly created and used can approach optimal efficiency (where the removed of solids from the mud system equals the influx of drilled solids). Every piece of solids-control machinery is made to filter out particles according to their size or specific gravity. Shale shakers, desanders, desilters, hydrocyclone centrifuges, and bowl centrifuges are some of the solids control devices now in use.
The vibrating screen of a shale shaker separates drilled solids coming to the surface from the mud stream. The size of the screen opening, which ranges from a 10*10 mesh to a 200*200 mesh, is determined by the amount of mud that is circulated. To remove massive drilling cuttings, the majority of shakers on rigs have a mesh size of 10 to 20. Some drilling rigs have recently switched to shakers of the current variety with smaller mesh screens. These smaller screens remove a greater portion of the drilled solids from the mud stream, although they are constrained by the handling capacity of the circulating volume.
The most popular solids control devices after the shale shaker are hydrocyclones such desanders, desilters, and mud cleaners (shaker, desander, and desilter combined). They are made to extract drill solids with low specific gravities and particle sizes of 20 m and larger. The desilter can remove sand-size particles down to around 20 micron, while the desander may remove particles as small as 45 micron. A monograph may be used to assess the hydrocyclone’s performance in the field (Fig 2.). The weighted mud system is processed using this machinery. Barite is eliminated by itself with drilled solids of low specific gravity. Due to the high expense, using desanders and desilters on weighted mud systems is impracticable.
In a weighted mud system, hydrocyclone centrifuges and bowl centrifuges offer an affordable way to remove colloidal-sized particles smaller than 10 microns without wasting useable barite. When hydrocyclone and bowl centrifuges are utilized on a weighted mud system, some barite will still be lost. The ultrafine nature of this barite, on the other hand, results in stronger rheological qualities.