Water control is the key to prolong well life for economical and efficient oil recovery. When water reaches certain levels, oil production profitability decreases dramatically and even goes to negative. One feasible option in this case is a rigless water shut-off treatment, which involves an intensive process, starting from candidate selection and finishing with post-treatment well performance analysis. This kind of operation becomes more challenging for horizontal wells with open hole completion. Well A, a horizontal open hole producer with 2,440 ft of reservoir contact, was drilled and completed in November 2000. The last well production profile was determined by a Flow Scan Image (FSI) log, which showed 51% of water cut and the entry of most of the water was from the toe of the horizontal section. Based on economical and technical feasibility, fiber optic telemetry enabled coiled tubing (CT) was selected for an accurate and effective way to isolate the water producing interval, reduce water cut and enhance oil production. The advanced and intelligent CT enables real time downhole measurements via fiber optic telemetry system. The system consists of surface readouts including dynamic interpretation software, fiber optic cable, and bottom-hole sensors, which provides Casing Collar Locator (CCL) readings, Distributed Temperature Survey (DTS), temperature, internal and external CT pressure measurements. Permanent zonal isolation, utilizing an inflatable packer with a cement plug above the packer, was successfully performed using CT conveyed fiber optic system. The availability of CCL, temperature and differential pressure readings enabled precise depth control, proper packer inflation and optimization of the cement design. This paper highlights the application of a CT equipped with fiber optic advanced technology on a rigless water shut-off job. The paper also discusses the water shut-off (WSO) job design and execution challenges. Introduction Drilling horizontal wells become the norm in many Saudi Aramco fields. As horizontal wells mature, oil rate is reduced due to increasing water production, which dictates the need to perform water shut-off jobs to sustain oil production.

Water production is a serious challenge when stimulating wells in mature reservoirs. Production results after acidizing sometimes reveal a higher water cut; in some cases this change is significant enough that the well is no longer able to flow unassisted. A typical acid stimulation in the field follows a predetermined pumping schedule, where diverter is squeezed into the high water cut interval prior to injecting acid into oil zones. The diverter volume is based on a rule of thumb and the acid is pumped after assuming that the diverter is efficiently sealing the high water cut zone. Several coiled tubing (CT) matrix stimulation jobs have yielded production results of 100% water cut.Prior to stimulation (a period of months or years), diagnostic logs were conducted to identify water producing intervals. Although, in some cases, the post-stimulation water cut may be as high as or higher than the water cut prior to the stimulation, suggesting that the diverter volume was not enough to seal the water zone. An innovative method is needed to confirm the isolation of high water cut zones before pumping acid, which would lead to increased oil production and reduce the risk of unintentionally stimulating water producing zones.

Te oil producer wells, in the southern are of Saudi Arabia, are mostly completed as horizontal open hole (OH). Some of these wells are dead or on itermittent production due to high water cut, which is caused mainly by water influx through carbonate fissures or fractures. Multiple water shut off (WSO) jobs using inflatable packers, were performed between 2005 and 2010 but failed during execution because of the packers setting failure in OH. The WSO candidate selection process starts with reservoir and production data evaluation, then requires a coiled tubing logging run to identify the water source and adjust the required isolating fluids formulation and volume. For the execution, there is a need to control the placement, inflation, injection and disconnect of the inflatable packers in order to ensure successful WSO treatment. This paper describes how the fiber optic enabled coiled tubing (FOECT) system, enabling realtime downhole data measurement, can optimize the WSO treatments design, execution and evaluation, and increase their success rate. For the job design, production logging tools were run with FOECT string to detect the water source, measure the BHT required for the formulation of WSO fluids, obtain a GR log, and get an X-Y OH caliper critical to decide the best setting depth for the inflatable packer and to confirm the required WSO fluids volume. For the job execution, the depth correlation for the packer setting was performed with the fiber optic bottom hole assembly FOBHA-GR. The inflation of the packer and the injection through it were monitored and adjusted realtime with the FOBHA-PTC measurement inside and outside the FOCT string. The confirmation of the packer setting and the release from it were confirmed with the world's first applications of FOBHA-Tension/Compression sub. Recent production results showed previously dead well flowed at significant oil rate with 10% water cut after performing a WSO with FOECT innovative solution. The integrated FOECT solution, eliminating engineering assumptions during the full cycle of design-execution-evaluation, is a proven WSO technique in OH, which can bring many wells back to economical production.

Stimulation of wells completed in multiple layers has always remained a challenge with regards to stimulating all the layers uniformly and effectively. Problems are more severe if the sub-layers of the formation have different petro-physical characteristics and have varying degree of permeability contrast. Stimulation treatments without diversion system applied in these multi-layered wells mainly stimulate the high permeable streaks repeatedly. PH and temperature sensitive In-Situ Cross-linking Acid Diverting Agent (ISCADA) is developed to temporarily block the high permeable or undesired layers. This diverter chemical with maintained pH is cross-linked in-situ at reservoir temperature. Breaking time of the diverter could be tailor-made by optimizing the breaker depending upon the requirement of treating time. The diverting agent has the advantages of breaking on its own and clearing the blockage of the high permeable zone to regain its initial permeability while facilitates the acid to stimulate the desired zones. The alternating stages of diverting agent, retarded acid and main acid can be designed as per the well conditions. ISCADA can be applied in both sandstone and limestone reservoirs. Trial application of ISCADA system was done in the limestone formations of Mumbai high field and other sandstone reservoirs. Substantial improvement in productivity observed using ISCADA as diverting agent and subsequent application of compatible acid formulation. Remarkably water production has come down in some wells. This paper outlines the laboratory development of the diversion stimulation system; case histories of its application in limestone and sand stone reservoirs. Introduction Stimulation of multi-layered wells has always a remained challenge with regards to uniform and effective stimulation of all the layers. Stimulation treatments without diversion system applied in these heterogeneous multi-layered wells mainly stimulate the high permeable streaks repeatedly leaving other layers untreated. With the aim of stimulating the multi-layered wells uniformly, efficiently and cost-effectively an acid diversion system is essential. In the context of Indian reservoirs diverting acid into untreated zones has remained great challenge in the thick, and high permeability onshore sandstone formation as well as multi-layered carbonate formations in the offshore. Diversion is the process by which the treating fluid is diverted from high permeable zone and allowed to enter the lower permeable zone, thereby making the homogenous distribution of treating fluid in the zones of interest. A critical factor to the success of an acidization treatment is proper placement so that designed volumes of treating fluids contact productive intervals. Effective placement of the treating /stimulation fluids evenly across the zones of interest is important specially when treating long perforated intervals or multiple zones. If there are significant variations in reservoir permeability, the acid will tend to flow primarily into the highest- permeability zones, leaving lower- permeability zones virtually untreated. Even in relatively homogeneous formations, the damage may not be distributed uniformly without the use of techniques to improve the acid placement; much of the damage may be left untreated. Thus the distribution of the acid into the formation is an important consideration in matrix acidizing, and treatment design should include plans for uniform acid placement. The in-situ cross-linking acid diverting agent (ISCADA) is both pH and temperature sensitive. This diverter chemical with maintained pH is cross-linked at reservoir temperature. The cross-linked, high viscous diverting agent then blocks the subsequent treating fluid to enter into the high permeable layer and divert them to the zone of interest. The alternating stages of diverting agent, retarded acid and main acid can be designed as per the well condition. This paper discusses the laboratory development of the ISCADA and general guidelines for implementation.

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.