This paper was a repeat presentation at the SPE Middle East Oil Technical Conference and Exhibition held in Bahrain, 3-6 April, 1993.

Abstract

During 1991 ADMA-OPCO planned to drill two horizontal producers. It was also planned to measure the petrophysical properties of the horizontal sections by Logging While Drilling (LWD) and by conveying conventional open hole logs on drill-pipe under Tough Logging Conditions (TLC). Each well was suggested to be logged by different LWD contractor.

Bullheading the acid into the formation is very inefficient and not expected to stimulate more than a few feet of the horizontal section as the acid tends to spend near the top when it contacts the limestone formation. Thus, to allow uniform distribution of the acid in the horizontal sections, the coiled tubing was used to pump the acid into the formation while pulling ft out.

Batches of foam diverters were pumped at regular intervals to ensure proper diversion of the acid. During the pumping sequence, a diesel oil was pumped down the coiled tubing X production tubing annulus to prevent the injected fluids from travelling up the hole by creating a back pressure on the upper sections.

Part one of this paper reviewed the logging operations and compared the results of the two LWDs with the open hole logs and with the core analysis results.

Part two discussed the operational and efficiency aspects of stimulating an offshore horizontal well.

INTRODUCTION AND OBJECTIVES (Part 1)

The wells "A" and "B" were located on the northeastern and east-southeastern parts of the field (fig. 1). They were originally drilled as deviated dual producers. They were closed-in later due to mechanical or mainly water influx problem.

Based on the above production difficulties, it was determined to work-over the wells and complete them as single horizontal producers.

The objectives of the first part of this paper are the following :

  • To discuss the logging operations ran while drilling (LWD) and those accomplished under Tough Logging Conditions (TLC).

  • To compare both types of logs in terms of resolution, reliability, differences and relevance.

DRILLING THE HORIZONTAL SECTION

After long down hole operations, the old completions were recovered and the wells were prepared for horizontal drilling. The kicking-off has taken place, respectively through a window in the 9 5/8" casing and upper formation where new 8 1/2" holes were opened. The total depths were successfully reached and the wells have achieved their planned targets.

a. Well "A"

The reservoir engineers recommended opening two horizontal sections through the reservoir. The upper one should range between 37-45 ft. below the reservoir top, fig. 2.

The lower horizontal section was required within 51–63 ft. below the top of the reservoir (fig. 2). The length of the horizontal sections were required to be 1500 and 500 ft, respectively. So, upon the reservoir engineering requirements, the horizontal well trajectory was designed as displayed in Fig.3.

Table 1 and Fig. 4 show some actual details of the horizontal section whereas the cored intervals and recovery are indicated in Fig. 5.

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