Field development costs have risen with oil price. A resulting challenge with Arab heavy oil development remains how to generate competitive advantages through deploying efficient technological innovations and making cost-effective solutions a crucial part of a firm's strategy for rigless interventions. With strict commitments to environmental protection, the need for operational excellence and several process improvements necessary to yield dividends in the form of safe project delivery and to overcome several technical difficulties is vital. The scope of the paper is to examine coiled tubing (CT) stimulation and logging technologies used in the timely project execution of one of Saudi Arabia's largest field developments to cost effectively enhance matrix stimulation success. Some of these solutions include technologies for CT reach, CT access for dual laterals, acid placement optimization, and treatment effectiveness monitoring. CT extended reach solutions comprised tapered CT strings designed for ultradeep wells, drag reducers, tractors, and vibrators. Technologies for CT access for dual laterals include a flow activated multilateral tool for CT matrix stimulation employing pressure variation telemetry with bottom hole pressure (BHP) and casing collar locator / gamma ray (CCL/GR) for high success lateral identification. To optimize acid placements, distributed temperature survey and pressure measurements are used to enhance diversion and acid placements. A blend of tools assisted to monitor, analyze, and adjust in real-time the reservoir and stimulation fluids interaction. Viscoelastic diverting acid is designed to viscosify in situ as the fluid spends on the reacted formation for chemical diversion in carbonates. The concentration of the diverter was optimized from 20% HCl to 15% HCl. A unique solution for monitoring treatment effectiveness evolved to include real time production logging using single strings for CT stimulation and real time profiling instead of memory logging. This solution required less equipment mobilization and no wireline unit. Intervention from 99 producers and injectors reveals operational and cost benefits from deploying technological solutions and justifies the degree to which each technology solution fits the overall field development strategy. The implications of deploying these solutions include reduction of well counts from the original estimates in this field development to offer manageable total field development costs.
With the growing demand for oil production, and pressure maintenance for giant fields, more horizontal wells has been drilled as power water injectors and oil producers to increase the contact with the reservoirs. In M-field, many wells are drilled as mega-reach with a measured total depth up to 33,000 ft. This present a big challenge for coiled tubing intervention to reach TD and stimulate or perform logging. Even with the use of hydraulic tractors, CT Pipe Locks up before TD, and it has been difficult to understand the root cause as it is not possible to differentiate between a hydraulic tractor malfunction and downhole obstruction causing the CT to tag. Here in this paper we are going to illustrate the reach challenges, analysis performed on the un-anticipated lockups, and how could we utilize recent technologies in understanding the lockup occurrence, as well as quantifying the how can we improve the prejob tubing force model simulation to fine-tune well accessibility in real-time while on the job. With the implementation of the real-time tension-compression tool, it becomes possible to detect any malfunction of the hydraulic tractor. With the real-time reading of the tractor pull downhole, the coiled tubing force model simulation can be adjusted during the operating to match the real coiled tubing weight and have better estimation of the expected lockup depth. Real-time informed decisions can optimize the CT reach. Being in ultra heavy oil formation and barefoot completion, the following questions come to the scene: Are we tagging in tar? or it is just the excessive drag force that is causing an early lockup?; What if the tractor fails? and how to diagnose the failure?; Shall we use solvents? at what quantities if any?; Is it feasible to run more than once? or it is a challenge that we cannot overcome? All the above questions are answered in details in the paper with illustrated troubleshooting, and problem solving workflow that is aided by case studies, jobs results, and success stories from one of the biggest fields in the Middle East. Exploring more in this direction would successfully change the face of the tubing force model simulation algorithms and take the on-site operational excellence to a significantly advanced level.
Success of matrix stimulation treatments depend on the uniform distribution of treating fluids over the entire production/injection interval. Thus, when acid is pumped into a well, it naturally flows to the most permeable/least damaged zone. To avoid improper placement of acid into one interval of a zone of different injectivities, diversion techniques can be applied. Diversion can be accomplished by either mechanical means or chemical means.Diverting chemicals are deposited over the perforations or the formation. When deposited, they form a layer with a lower permeability than the formation it is covering. This imposes an additional pressure drop needed to penetrate the cake will cause the fluid to divert to another part of the perforated interval. Eventually, uniform injection is accomplished across the whole interval.Different concentrations of diverting agents can be used to get the required diversion, but how to know if the diverter pumped is indeed diverting or not is a challenge. Bottom-hole pressure or temperature responses can be checked during the job to get an idea if diverter is working properly. Thus, Fiber Optic Enabled Coiled Tubing with Fiber Optic Enabled Bottom-hole Assembly (FOEBHA) with pressure and temperature sensors for real-time downhole measurements and Distributed Temperature Sensing (DTS) is the best solution available. This paper describes the use of different concentrations of diverter i.e. visco elastic diverting agent and the behavior responses of downhole parameters with their usage.
Successful stimulation fluid placement in extended reach wells (ERW's) through coiled tubing (CT) is primarily dependent on the depth reached for maximum reservoir contact. Well configurations of minimum bypass (2.4 in.) and openhole sections (6 1/8 in.) are the main challenges for CT reach in these ERW's. Implementation of a CT slim tractor along with fiber-optic enabled cable were applied to overcome the challenges and set a new record for CT reach. CT lockup is the phenomenon that occurs due to friction forces and helical buckling, which limits the CT reach. To tackle these challenges, an accurate simulated lockup depth is estimated using historical data to identify the required pull force. The CT slim tractor (2 1/8-in.) was chosen as the optimum tool to provide the required pull force, as well as pass through the minimum ID restriction of the well. Specially designed tapered CT with fiber-optic enabled cable acquired real-time data from the downhole tension-compression (TC) sub to confirm both the activation and lockup depth of the tractor. The expansion ratio of the tractor from 2 1/8-in. to 6 1/8-in. OH section opens a new era for CT reach in restricted ERW's. The world slimmest tractor passed the 2.44-in. minimum ID restriction and provided more than a 3,000 lbf pulling force, allowing the CT to cover the entire openhole section. Along the way, two new records were recorded for the longest section tractored by a slim CT tractor and the furthest distance travelled in a producer well reaching a TD of 24,706 ft. Increased reservoir contact during stimulation through engineered solutions has set a new standard enabling the implementation of a full stimulation campaign. These engineered solutions demonstrate the potential for CT interventions in extended-reach horizontal wells with completion restrictions, where the main challenge is to maximize the reach for optimum stimulation. As a direct result of several innovative solutions applied simultaneously, a new record for CT reach was set, surpassing the previous record by nearly 5,000 ft.
As a result of the continuous development of drilling technology, more complex wells can be drilled to overcome reservoir challenges and reach target intervals. Over the last decade, innovative drilling techniques have enabled a significant increase in the number of multilaterals and extended-reach wells; this imposes new challenges regarding well accessibility for rigless intervention techniques, which has driven operators, manufacturing, and service companies to develop innovative strategies for servicing these fields. In Saudi Arabia, one extended-reach power water injector (PWI) well was sidetracked to enhance injectivity. During the sidetrack, it was necessary to drill more than 1,000-psi overbalance due to the presence of high-pressure zones across the horizontal section, which resulted in formation damage on the low-pressure intervals. Based on this situation, a well intervention plan was considered which would use Coiled Tubing (CT) acid stimulation to remove the formation damage especially toward the end of the open-hole horizontal section. This operation involved two particular challenges; the first of which was the CT reach across the open-hole section, especially when CT forces simulation predicted a maximum coverage of 50% of the target zone. The second challenge was implementing the proper jetting tool to be able to function with the combination of the downhole tractor and high rate acid stimulation to ensure penetration across the filter cake and remove formation damage in the entire target zone. In order to make this solution feasible a specially designed downhole tractor was engineered, manufactured and incorporated with a newly designed high pressure jetting tool to be able to have full functionality of the downhole tractor while still performing full high rate stimulation to penetrate the damaged zones. This paper describes the combination of slim tractor and high-pressure jetting tool to conduct an effective acid stimulation job in an extended-reach PWI and have a CT reach of 98% instead of the predicted 50% reach in one of the major carbonate reservoirs in the Saudi Arabia. In addition, this paper provides design methodologies, best practices and industry lessons learnt from the experiences gained in the implementation of multi-purpose tool solution in Saudi Arabia.
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