The M field development involves one of the largest drilling projects in Saudi Arabia, targeting various carbonate reservoirs, and with an extraordinary amount of extended reach wells (ERWs) requires meeting the expected oil production rate, at the lowest development cost possible. More than two-thirds of the wells fall under the extended reach drilling classification, and the majority of the wells have measured depths (MDs) between 24,000 ft and 31,000 ft. These wells are open hole completions where acid stimulation is highly needed to overcome reservoir damage and improve the well's performance after drilling operations terminate.The placement of the treatment fluids requires a uniform distribution along the open hole section. Among the different techniques considered, namely bullheading, using the rig drill pipe and coiled tubing (CT), the last one offered the soundest technical and cost option. However, the CT technique alone did not show the ability in reaching the maximum depth in most ERWs of this field. Therefore, the tractor 1 was required to provide the significant amount of pull force needed to operate inside these long distances, not seen before in open hole completions.The first eight well campaigns, using a combination of CT, a hydraulic tractor and friction reducer fluids, have achieved the main objectives. Moreover, a new intervention world record 2 was set when the CT bottom-hole assembly (BHA) reached the maximum depth of 28,257 ft inside open hole in two different occasions, to place the stimulation fluids, and to record an injection profile. During the campaign, a total of 41,774 ft accumulated footage has been operated with the tractor, allowing over 3,400 bbls of acid to be placed in direct contact with the formation. As a result, the average injection rate has increased more than tenfold, reducing the drilling requirements for injection wells originally projected.The job preparation, technology, results, learning curve experience and best practices are discussed in this paper, including proposed operational enhancements. This experience demonstrates the feasibility of the operations with CT required for full zone coverage, yielding optimum water injection rates at the lowest development cost.
TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractStimulation of oil wells is becoming more and more challenging every year. Wells easy to select are fast diminishing. Today's candidate for matrix acid stimulation have high water cut, close oil-water contact, marginal pay zone to stimulate and complex completion, raising more challenges. Combining coiled tubing pinpoint treatment placement with diversion method is crucial for such wells. Traditional chemical diversion like gelplug, VES, foam or nitrogen divert treatment fluid in the zone of broad permeability contrast.Interestingly, encouraging results were experienced when coiled tubing coupled with downhole rotary jetting tools were used to augment chemical diversion. For the first time these tools have been used to facilitate stimulation of openhole completed wells in carbonate reservoir of Ghawar field with outstanding result.Rotary jetting tool is useful mechanical mean to supplement coiled tubing pinpoint placement of stimulation fluids due to high power jetting and 360 degree rotation of the jetting tool. The high pressure drop across the nozzles is converted to high velocity flow which penetrates deeply and thoroughly inside the critical matrix and improves the quality of the treatment placement. Based on well conditions, proper nozzle size with optimized jetting power by speed-controlled rotating nozzle head is the key in this process. Significance of this system is to eliminate the domination of the high permeable zone on the treatment distribution by improved pinpoint jetting efficiency with proven results. It reduces the treatment fluid volume per foot of formation. Sustained gain is achieved as the treatment is more than acid wash. The system also replaces traditional jetting and wash-tools that are without rotating capacity. This paper evaluates the added value of high velocity downhole rotary jetting tools in pinpoint acid stimulation operations with all pros and cons. Case studies for both oil producers and water injectors will be discussed.
The implementation of multilateral wells in Saudi Aramco, and in the southern area of Ghawar field in particular, is being increased for production and cost optimization. Accessing and stimulating individual laterals is a challenge that requires an optimum design in terms of cost, application and efficiency. This paper will describe a unique utilization of a combined high energy rotary-jetting tool with a multilateral tool (MLT) to access and treat a dual-lateral oil producer in the southern part of Ghawar field. The main purpose of utilizing this combined tool was to acid wash the Arab-D horizontal section of both laterals with nitrified hydrochloric acid using coiled tubing (CT). The objectives of the treatment were to increase flowing bottom-hole pressure (FBHP), remove formation damage and return the well to production. The rotary-jetting tool is a high energy jetting tool that maximizes performance of treatment fluids while minimizing the need for large acid volumes. It can be run with the MLT to enable accessing and stimulating both laterals in a single trip. The implementation of the combined tool resulted in accessing and stimulating both laterals successfully. The well was returned to production at a rate of 11,000 barrels of oil per day (BOPD). The volume of acid was reduced due to utilizing the rotary-jetting tool, which maximized fluid treatment performance. This paper will cover the whole cycle of candidate selection, job design, execution, post job evaluation and conclusion. Introduction Oil drilling strategy in the world as a whole, and Saudi Arabia in particular, has shifted drastically from drilling vertical wells to drilling horizontal and multilateral wells. This increasing trend is a result of enhanced productivity provided by maximizing reservoir contact. These wells have proven successful and economical for field development in oil and gas fields. Although drilling practices and experiences have drastically progressed, there are still limitations on the accessibility of the laterals for treatment or logging. During the past few years, there was a considerable advance in rigless re-entry techniques. The well intervention work can now be conducted on an individual lateral as a result of utilizing the MLT re-entry tool with CT pipe1, 2 & 3.
With the increasing complexity of well completion, the rigless intervention work is becoming more challenging. Conventional techniques are no more adequate to access long horizontal wells to perform intervention work such as acid stimulation, logging, and zonal isolation. This paper will describe the process of using a downhole coiled tubing (CT) tractor to access a horizontal open hole (OH) extended reach power water injector (PWI) well in the Ghawar field, the world's largest oil field, to perform a huge matrix acid stimulation job. The volume of the treatment is considered one of the largest for a PWI and the first utilization of a CT tractor in the Ghawar field. The paper will review the process of candidate selection, job design and planning, execution, and results and post job evaluation. The job set an excellent example of advancement in intervention technique accessing long horizontal wells beyond the normal reach of coiled tubing. In this job, the CT tractor has increased the reach of CT by 54% and a world record of coiled tubing tractored interval in horizontal OH of more than 5,000 ft was achieved. The injection rate of the stimulated wells was increased by more than twofold. Introduction The giant Ghawar field, located in the Eastern Region of Saudi Arabia, is more than 200 km long and 40 km wide of carbonate reservoir with continuous oil column, Fig. 1. The production from the field was started in 1951 from the northern part and thereafter the field was developed toward the southern tip with the last increment put on stream in 20061. Reservoir characterizations change along the north-south lateral with the southern part known for lower reservoir quality dominated by low permeability fractured formation. To maximize recovery of oil from this unique reservoir, peripheral water injection was started in 19662. As the development reached the southern part of the Ghawar, the reservoir quality dictated the necessity to utilize the latest advancement in drilling technology including long horizontal, maximum reservoir contact (MRC), real-time geosteering, and I-Field initiatives. These complex completion wells present a challenge to production engineers to riglessly access them in order to perform intervention work to enhance performance or remedy downhole problems. Due to tightness of reservoir formation combined with formation damage, matrix acid stimulation jobs were deemed necessary to improve injectivity supporting the reservoir pressure in this part of the field. In extended reach horizontal wells, bullheading of treatment fluid is not efficient due to the nature of this fractured reservoir and a coiled tubing unit (CTU) should be used to provide uniform distribution of the acid across the horizontal treatment interval. Field experience indicated that accessibility of a CTU in horizontal wells is limited due to increased friction generated when the pipe starts to get helically buckled and finally reaches a lockup point where the total down acting forces are no more sufficient to move the CT pipe further in the well. This limits the capability to distribute the treatment across the horizontal section. Different techniques have been used to overcome this limitation of CT to perform intervention work such as using large outside diameter (OD) coiled tubing, downhole vibration tools, and friction reducer chemicals3, 5. Well Completion and History The well was drilled and completed as an extended reach horizontal OH PWI to a total depth (TD) of 17,716 ft and true vertical depth (TVD) of 7,690 ft, Fig. 2. The 6 1/8" OH was drilled from 8,322 ft to TD. The well was completed with 7" completion packer and a tail pipe assembly at 7,358 ft with the end of the tail pipe at 8,794 ft, leaving 8,922 ft of horizontally exposed reservoir formation with a maximum inclination angle of 93°. The average reservoir porosity is 10%. The objective of this completion is to cover the anhydrite formation in the 6 1/8" OH below the 7" liner to the top of the injection formation, Fig. 3. The decision to set the packer was taken during the drilling course due to unexpected formation development and dipping where the setting of the 7" liner was found above the injection formation leaving the anhydrite formation exposed.
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