TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAsphaltene deposits were obtained from three high gas/oil ratio (GOR) wells in an offshore field in the Arabian Gulf. The reservoir is saturated and there is a gas-cap present in the field. In many wells the gas cones into the producing wells and causes precipitation of asphaltenes from the crude by stripping. These asphaltenes deposit in the wellbore and have the potential to create plugging problems.This paper describes the results of an investigative study that was initiated to determine the precipitation mechanism and ways to alleviate the deposition problem. Asphaltene precipitation experiments were conducted at reservoir conditions in a special pressure-volume-temperature (PVT) apparatus. The effect of GOR on asphaltene precipitation was determined by titrating the reservoir oil with gas-cap gas. Bulk deposition tests were also performed at different GORs with reservoir fluids. The results demonstrate that the onset of asphaltene precipitation occurs at relatively low GOR values. The amount of asphaltene precipitated at the onset is small. Asphaltene precipitation and deposition increase with increasing GORs. Asphaltene deposition envelopes are provided for the reservoir oil as a function of pressure and temperature. Recommendations were made to alleviate the problem by controlling the maximum producing GORs to less than 1000 scf/stb. Recipes for solvent treatment including asphaltene dispersants are also described in the paper and are currently being considered for implementation in the field.

As the offshore Saudi Arabia fields mature, more wells are becoming wet and consequently more wells are dying due to water encroachment. These dead wells and associated facilities are valuable assets that need to be effectively utilized throughout the producing life of the fields. Therefore, remedial actions to revive dead wells are vital strategies to maximize revenues. Rigless water shut-off techniques in conventional wells have been successful due to relatively simple wireline interventions. However, water shut-off jobs in horizontal wells are more complicated and are more challenging tasks for oil companies, including Saudi Aramco, due to their associated high cost and cement placement uncertainties. This paper is a study of six years of rigless water shut-off efforts to revive dead wells in Saudi Aramco's Northern Area offshore fields to extend the producing life of the wells and enhance oil recovery. During the study period, 46 rigless water shut-off jobs were executed with a 91% success rate. Of the 46 water shut-off jobs, three jobs were successfully implemented on dead horizontal cased hole wells using coiled tubing (CT). The job success is attributed to proper problem diagnosis, job design and execution, resulting in a significant production gain and workover cost avoidance.

Injectivity of water disposal wells is decreasing with time as tar accumulates in the wellbore and/or within the vicinity of the wellbore. The tar deposit reduces and deteriorates the effective wellbore length in addition to increasing mechanical skin across the sand face. The injectivity of water disposal wells can be effectively enhanced/stimulated by doing special chemical treatment mainly for sand stone reservoir. This helps to reduce injection bottom-hole pressure and consequently increase the pumping rates. This proposed chemical treatment was used for the first time in Saudi Arabia for sandstone reservoir to remove tar accumulation. The chemical treatment fluid (recipe) was tested in the lab and showed promising results. In this trial test, a water disposal well candidate with a low injection rate was selected to be implemented for the trial test. The treatment was aimed at enhancing well injectivity and the initial results of the field implementation demonstrate a significant improvement in the injection rate. This result was confirmed from the rate measurement before and after the treatment in addition to well testing analysis. Key results were consolidated with fall-off tests conducted before and after the treatment proving the effectiveness of the chemical treatment at reducing the skin and increasing the injection rate. In addition, this chemical is cost effective compared to other chemicals previously used for the same treatment objective. This paper also illustrates the current procedures and provides recommendations for future job execution with new procedures and steps to improve results.

As the offshore Saudi Arabia fields mature, more wells are becoming wet and consequently more wells are dying due to water encroachment. These dead wells and associated facilities are valuable assets that need to be effectively utilized throughout the producing life of the fields. Therefore, remedial actions to revive dead wells are vital strategies to maximize revenues. Rigless water shut-off techniques in conventional wells have been successful due to relatively simple wireline interventions. However, water shut-off jobs in horizontal wells are more complicated and are more challenging tasks for oil companies, including Saudi Aramco, due to their associated high cost and cement placement uncertainties. This paper is a study of six years of rigless water shut-off efforts to revive dead wells in Saudi Aramco's Northern Area offshore fields to extend the producing life of the wells and enhance oil recovery. During the study period, 46 rigless water shut-off jobs were executed with a 91% success rate. Of the 46 water shut-off jobs, three jobs were successfully implemented on dead horizontal cased hole wells using coiled tubing (CT). The job success is attributed to proper problem diagnosis, job design and execution, resulting in a significant production gain and workover cost avoidance.