Since the advent of horizontal technology, new wells have been drilled with thousands of feet of horizontal section to expose large reservoir areas. The advancement of drilling technology also allows drilling more complex wells, such as multilaterals for maximum reservoir contact (MRC). These complex wells impose great challenges with respect to well accessibility for rigless well interventions. One of the initial well interventions, which follow drilling completion, is acid stimulation to remove formation damage. On the other hand, the recent advancement of coiled tubing (CT) enables rigless interventions of complex wells while acquiring real time downhole measurements. The fiber optic enabled coiled tubing (FOCT) provides combined services of data acquiring and running other CT tools required for well treatments. The fiber optic telemetry system consists of a pump-through bottom-hole assembly (BHA) with a casing collar locator (CCL), pressure and temperature sensors, optical fibers inside CT, and a surface readout unit. By the virtue of the optical fiber, distributed measurements are also viable options to obtain temperature profiles. The temperature surveys allow evaluating flow distribution through temperature responses, thereby optimizing acid stimulation. A multilateral tool (MLT) using an indexing flow activated bent sub allows locating and accessing the laterals and stimulating them. The CCL readings via the FOCT provide a real time confirmation of accessing laterals. This paper highlights the first worldwide CT application of combining the fiber optic telemetry system for acquiring downhole data on real time, and a multilateral tool for accessing and stimulating a trilateral oil producer in a major carbonate reservoir in Saudi Arabia. This combination has resulted in a successful optimized acid stimulation of all three laterals. This paper also discusses in detail the job execution challenges, lessons learned, and experience gained to optimize similar future jobs. Introduction Drilling horizontal wells become the more commonplace in many Saudi Aramco fields. Recent advances in drilling and completion practices enable us to drill more complex wells with various types and shapes, such as extended reach wells, bilateral, multilaterals, maximum reservoir contact (MRC), etc. Benefits of drilling these wells include reduction in development and operating cost because of the lower number of wells and improve the reservoir performance and management. These complex wells are drilled for various reasons and many objectives, which may include but not be limited to: increase production, enhance reservoir characterization, improve sweep, maximize recovery, and ensure efficient reservoir management1, 2.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractHorizontal, extended-reach, and multi-lateral wells are drilled to maximize production from oil and gas reservoirs. Treating these wells with scale inhibitor is a real challenge. This is mainly due to reservoir heterogeneity and chemical placement.Several horizontal wells were drilled in a sandstone oil reservoir. These wells were completed with 1,000 to 1,500 ft of pre-packed screens and produced wet crude with water-cut ranging from 5 to 30 vol%. The total dissolved solids of the produced water was nearly 8,000 mg/L. The bottom hole temperature is 152°F. The porosity varied from 5 to 30 vol%, whereas the permeability varied from 1 to 3,000 md.Calcium carbonate scale was detected downhole due to temperature and pressure changes that occur at the intake of the electrical submersible pumps. The scale was removed by an acid treatment. However, there was a need to develop a chemical treatment to mitigate scale in these horizontal wells.An emulsified scale inhibitor squeeze treatment was developed and applied in several horizontal wells in the sandstone reservoir. The emulsified inhibitor has high viscosity which decreases with the shear rate (shear thinning behavior). These rheological properties enhanced placement of the inhibitor across the target zone. Coiled tubing was also used to place the emulsified inhibitor, which also enhanced the placement of the inhibitor across the target zone. The treatments were successfully applied and no operational problems were encountered. Oil production and water-cut did not change as a result of the scale inhibitor (phosphonate-type) squeeze treatment. This paper will discuss the design of the emulsified scale inhibitor squeeze treatment, field application, and analysis of produced fluids.

Proven to maximize hydrocarbon production or well injectivity, horizontal multilateral completions have witnessed growth both in number and complexity over the years. These well types brought challenges with respect to well accessibility for rigless well intervention, and the ability to access these wells has been developed using coiled tubing (CT) to enable operations, such as reservoir stimulation, to be carried out. One of the main challenges is to identify and access each lateral, to be able to perform the stimulation to maximize well production. This challenge has been encountered in Saudi Arabian multilateral wells, which are drilled in a carbonate reservoir with an open hole (OH) completion and where the laterals are typically left with a high formation damage (skin effect) after drilling, thus requiring stimulation to improve their performance. At present there is no single technique for lateral identification without tagging TD. In this paper we describe how a combination of multilateral tool (MLT) along with CT downhole measurement system is used to locate and access laterals, selectively acquiring a gamma ray profile across each of the laterals, then optimizing the stimulation operation using distributed temperature survey (DTS) measurements. This paper discusses the planning, execution and evaluation of the results in a stimulation job performed on an open hole multilateral water injector employing a CT with fiber optics that enables a real-time downhole measurement tool (pressure, temperature, casing collar locator, gamma ray) and MLT. The results highlight the effectiveness of the technique in maximizing the wells performance.

The study well was first drilled as single lateral Power Water Injector (PWI), then sidetracked as a multilateral injector with a total reservoir contact of 23,094 ft. The well was completed with three new laterals all placed up-dip in the water leg. This geometry was specifically intended to increase injection potential and provide more pressure support in the lower transmissibility areas of the well's complex, carbonate field. This paper discusses the Coiled Tubing (CT) accessibility challenges, technology deployment and lesson learned for stimulating the first quad-lateral extended reach PWI ever drilled in the study area in Saudi Arabia. The PWI is used to increase the injection capacity and provide extra support to reservoir pressure. Due to the challenging extended reach well trajectory, technology unavailability, challenge of effectively access all 4 laterals and properly identify each later to stimulate them, CT with real time downhole monitoring was used in conjunction with a multi-lateral tool access. The multi-lateral tool (MLT) was used to provide controlled, oriented mapping to access each lateral independently. The indication for the correct lateral was confirmed by both downhole pressure drop across the multi-lateral tool. As all the laterals are extended reach, getting to total depth (TD) was challenging for some of the laterals even after implementing all the reach techniques. In order to be efficient and identify which lateral was accessed an innovative method was developed by using Gamma Ray (GR) tool and casing collar locator (CCL) to properly identify each lateral before having to reach TD to determine the lateral accessed. Once the proper lateral is accessed and determined, the acid treatment placement was pinpointed to and optimized by distributed temperature survey (DTS), which helped determine in real-time high permeable thief zones and tight or damaged zones. The treatment schedule was designed to divert from high intake zones using viscoelastic surfactant diverting acid system, followed by hydrochloric (HCl) acid for stimulation. The intervention was completed successfully without any safety incidents. The use of GR, CCL and downhole pressure & temperature measurements in conjunction with MLT tool gave the ideal method for lateral access and lateral confirmation especially when reaching to Total Depth (TD) was not feasible due to CT lockup. In addition the use of DTS for optimum stimulation placement was the key in improving operation efficiency. The methods developed in this paper on how downhole measurements such as pressure inside and outside CT and it's differential, CCL, GR, MLT and DTS can be used in Multilateral wells has proven to be a major success. This first intervention of its kind has opened new innovative ways and techniques of confidently stimulate all the multilateral extended reach wells in Saudi Arabia.