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A New Solids-Free Non-Damaging High Temperature Lost-Circulation Pill: Development and First Field Applications
Samuel, M. (Schlumberger) | Marcinew, R. (Schlumberger) | Al-Harbi, M. (Schlumberger) | Samuel, E. (Schlumberger) | Xiao, Z. (Schlumberger) | Ezzat, A.M. (Saudi Aramco) | Khamees, S.A. (Saudi Aramco) | Jarrett, C. (Saudi Aramco) | Ginest, N.H. (Saudi Aramco) | Bartko, K. (Saudi Aramco) | Hembling, D. (Saudi Aramco) | Nasr-El-Din, H.A. (Saudi Aramco)
Abstract Excessive loss of high-density brines into the formation has always been a major concern during completion operations, since it leads to formation damage and well control issues. The problem becomes more complex at high temperatures and when the treatment involves running gravel-pack assemblies and downhole sand screens. Typically, the fluidloss-control pills are composed of very high concentrations of crosslinked polymers with or without bridging particulates. The sealing mechanism of these pills is a combination of viscosity, solids bridging, and polymer filter-cake buildup on the porous rock. Due to the instability of polymers at high bottomhole temperatures, incompatibility with some divalent brines, and the necessity to cleanup with acid, a new solids-free lost-circulation pill that is stable for prolonged periods at high temperatures was developed. This paper introduces the development and the first field application of a new solids-free non-damaging viscoelastic surfactant-based fluid-loss pill (VES-PILL). The single-additive system forms a "gel" with most completion brines currently used in well operations. Laboratory data demonstrate that this pill could be used up to 375ยฐF. The "gel" structure of this system sustains viscosity high enough to effectively control or stop brine-loss, while maintaining a safe differential pressure into the formation. Several "frac and pack" completions were performed for the first time in Saudi Arabia in the Pre-Khuff sweet-gas zones. The VES-PILL was used to prevent losses after perforating, fracturing and gravel-pack operations. The pill was used in the field up to 310ยฐF, and brine-loss was effectively controlled for more than 3 days. The effectiveness of the pill was also demonstrated by a five-fold increase in surface pumping pressure during placement. The wells were produced at rates exceeding expectations without further remediation to cleanup the fluid-loss pill. Background Fluid-loss control is very important in successful well completion operations. Loss of completion and workover fluids is unacceptable due to economic (expensive heavy brines), technical or safety reasons (formation damage, hole collapse and well control issues). Loss of dense brines into the productive zones is highly damaging, especially to high permeability formations. It is very difficult to unload heavy brines once losses have occurred. Because of the high-density of brines used, stratification tends to further inhibit its removal. Calcium and zinc bromide brines can form stable acid insoluble complexes when reacted with some formation brines. Hence, the most effective means of preventing the formation damage is to limit completion brine losses into the formation by either chemical or mechanical means. It is best to avoid the use of fluid-loss control pills by incorporating mechanical fluid-loss control devices into the completion string whenever possible. However, in the absence or failure of such devices, or in situations where they cannot be used, chemical fluid-loss pills are required. The use of a pill is normally required before and after sand control treatments and after perforating. In these treatments, the pill is spotted into the perforations or against the sand control screens. In addition, fluid-loss control pills are required in several workover operations that need temporary zonal isolation. There are several reviews on the use of different types of fluid-loss pills and guidelines on the selection of the pill. A variety of fluid-loss control pills have been used in the industry, such as foams, oil-soluble resins, fibers,5,9 acid soluble particulates, graded salt slurries, high concentrated linear and crosslinked non-biopolymers and bio-polymers. The polymer systems are very effective in fluid-loss control as long as the temperature limit of the specific polymer is not exceeded. One of the important features of any fluid-loss pill is its ability to maintain viscosity under bottom-hole conditions (especially high temperature). The viscosity reduction of gel at high temperatures is either due to the degradation of polymer or reduced molecular interations. The viscosity will not be regained on cooling if there is molecular degradation at high temperature.
- Europe (1.00)
- North America > United States > Texas (0.93)
- Asia > Middle East > Saudi Arabia (0.66)
- Well Drilling > Pressure Management > Well control (1.00)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (1.00)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid management & disposal (1.00)
- Well Completion > Completion Installation and Operations (1.00)
SPE Member Abstract The main objective of horizontal drilling is to place a drain-hole within the pay zone for a long distance to enhance productivity or injectivity. In Saudi Arabia, horizontal wells have been successfully drilled through reservoirs with different characteristics such as tight to highly permeable limestone, extremely porous and permeable dolomite and dolometic limestone, and highly permeable unconsolidated sandstone. Based on laboratory test data, nondamaging fresh water and salt-saturated/polymer systems were selected for drilling the carbonate pay zones and a special oil-based fluid was developed for drilling the sand reservoirs. These drilling fluids satisfied the same basic functions common to all drilling muds and provided excellent reservoir protection. Production rates of the completed wells have reached several fold higher than the vertical producing wells from these reservoirs without stimulation treatments. This paper presents the laboratory data generated and discusses the fluids formulations and design criteria. Introduction High angle and horizontal hole drilling are difficult to achieve, but the present state-of-the-art technology is sufficiently well developed that each can now be performed with a satisfactory degree of confidence. Major drilling problems such as poor hole cleaning, excessive torque or drag, wellbore instability, stuck drillstring, loss of circulation, subsurface pressure control, poor cement jobs, difficulties associated with running electric logs and formation damage can result if the drilling fluid is poorly designed or executed. In order to design the best suitable drill-in fluids for Saudi Aramco horizontal wells, the drilling problems generally encountered in each field were studied and similar horizontal drilling projects worldwide were reviewed. Then, laboratory tests were planned and conducted to study the reservoir rock and fluids characteristics and select the most suitable and economical fluid formulations. The effective pore size distribution and morphology of each reservoir rock were examined and flow tests were run on core samples taken from each reservoir to determine the residual damage caused by several candidate fluids. Non-damaging clay-free, fresh water and salt-saturated/polymer systems were developed for drilling the carbonate pay zones and a special nondamaging oil-based fluid was formulated for drilling the sand reservoirs. Twenty-one wells have been successfully completed at this time. The horizontal hole section inclination ranged between 87 degrees to 90 degrees (maximum inclination recorded was 96.8 degrees). The horizontal length ranged between 1500' (591.59 m) and 3200' (701.01 m). Thirteen wells have been completed in carbonate reservoirs (open hole completions - producers, injectors and disposal wells). Eight wells have been completed in sandstone reservoirs with liner set and cemented in the horizontal section. A slightly acidic clean water or brine treated with a water wetting surfactant was used for completion and wellbore clean-up in the carbonate reservoirs. For the sandstone reservoirs, a clean water treated with an anionic surfactant and mutual solvent was used as perforating/completion fluid. This completion fluid prevents and/or breaks emulsion, cleans the oil-based mud residue and water wets the perforation tunnels. P. 645^
- North America > United States (1.00)
- Asia > Middle East > Saudi Arabia > Arabian Gulf (0.30)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > Asia Government > Middle East Government > Saudi Arabia Government (0.56)
- Asia > Middle East > Saudi Arabia > Arabian Gulf > Hanifa Formation (0.99)
- Asia > Middle East > Saudi Arabia > Arabian Gulf > Hadriya Formation (0.99)
- Asia > Middle East > Saudi Arabia > Arabian Gulf > Arabian Basin > Arabian Gulf Basin > Khafji Formation (0.99)